Today, one of the most widely used sample preparation methods is solid-phase extraction (SPE) that in the mid 1990s largely replaced the conventional but time consuming liquid-liquid extraction (LLE). The SPE method resembles chromatography itself: a liquid sample is passed through a packed column that selectively removes interferences or analytes.

The SPE sample preparation technique is frequently carried out in a small, disposable, plastic column (cartridge) that looks like a 10-mL medical syringe. The column is packed with a small amount (< 1.0 g) of sorbent (e.g. C₁₈-silica) which is held in place by frits.

Disposable cartridge for SPE (syringe style)

However, the SPE method can also be implemented by using a micro-pipette tip,  a 96-well plate, a disk, or even coated fibers, the later has its own name  - “solid-phase microextraction” or SPME.

SPE is typically used to:

• increase concentration of the analyte
• remove interferences (for complex organic sample matrix and also to protect the column)
• desalt (in ion-exchange chromatography)

Science and Life Magazine January 1890 (1)

by Dr. Viktorina Gruzdeva
Dec 31st, 1889

During the October 20th 1889 meeting of the Society for Public Health Protection, Dr. Kazanski presented a report on the making and chemical composition of “boza” (russ. буза). Boza is the name of a mongolian fermented beverage made from grains – a beer of sorts. As you know, beer is classified into 3 main categories, depending on the ingredients used: the first one is the oldest characterized by the absence of malt, the second category is made exclusively from malt, and the third kind which is something in between and requires both raw grain kernels and malted ones.
The second kind of beer is commonly used in Europe.  Although it has insignificant nutritional value, it can be stored for a long period and it has a much stronger intoxicating effect than other types. On the contrary, the first and the third kind of beer have significant quantities of nitrous substances and make an important nutritional supplement.

Turkestanian boza belongs to the third kind of beer. The main ingredient is raw grain; malt is used in the quantity only necessary for starch to turn into sugar. This Turkestanian boza is made from raw rice and millet malt.

Crimean Tatar boza belongs to the first type of beer: it is made entirely without malt, and solely from the wheat grain. Based on Dr. Kazanski’s research, here is the chemical composition of Turkestanian boza on the 3rd day of brewing:

Alcohol – 3.15% (by volume)
Extract – 8.18%
Nitrous substances – 2.15%
Lactic acid – 0.152%

If you compare these figures to beer from Petersburg’s breweries, you will find out that Turkestanian boza contains 1.5 less alcohol than regular beer, almost twice as much extract, 227 times more nitrous substances and 4.25 times more lactic acid. Moreover, boza also has 0.65% fat. Therefore, the nutritional value of Turkestanian boza is indisputable.

Crimean boza has a negligible amount of alcohol – no more than 0.25%; extract is up to 7.94%; nitrous substances found in the clear solution above the sediment – 0.5%, but the sediment itself has 12-14%. Hence, the nutritional value of Crimean boza is much higher than the Turkestanian one.

Scanning electron micrograph of strain GFAJ-1. Courtesy of Science/AAAS

Dr. Felisa Wolfe-Simon and collegues have discovered a microorganism that can live and grow entirely off arsenic. It is the first known published research that points to a bacterium that is able to use a normally highly toxic chemical rather than the phosphate to sustain growth and life.

Arsenic (As) is directly under Phosphorus (P) in the periodic table and they both share common chemical properties; however, arsenic is normally extremely harmful to living organisms because it disrupts major metabolic pathways. On the other hand, arsenate (AsO₄³⁻ – the oxidized As⁵⁺) is biologically very similar to phosphate. In the past scientists did find organisms that can chemically alter arsenic; and these organisms have been implicated in ground water poisoning events in Bangladesh and other places in Asia when people have shifted to using well water to avoid cholera.

Sunrise at Mono Lake © 2010 Henry Bortma

In their earlier research work, Wolfe-Simon, Davies & Anbar [1] hypothesized that ancient biochemical systems could have used arsenate in the equivalent biological role as PO₄³⁻ (phosphate). But now, Dr. Wolfe-Simon and colleagues have found a bacterium able to completely swap arsenic for phosphorus to the extent that it can even incorporate arsenic into its DNA[2]. The salt-loving bacteria, a member Halomonadaceae family of proteobacteria, came from the toxic and briny Mono Lake in California.

In the lab, the researchers grew the bacteria in vitro where phosphate salt was gradually replaced by arsenic, until the bacteria could grow without needing phosphate, an essential building block for various macromolecules present in all cells, including nucleic acids, lipids and proteins. Using radio-tracers, the team closely followed the path of arsenic in the bacteria; from the chemical’s uptake to its incorporation into various cellular components. Arsenic had completely replaced phosphate in the molecules of the bacteria, right down its DNA.

References:
1. Wolfe-Simon, Davies & Anbar Did nature also choose arsenic? International Journal of Astrobiology 8(2), 69-74 (2009).
2. This research appears in the 03 December 2010 issue of Science

Petechial rash on my ankle caused by RMSF (2004)

More than 3 years ago I shared a personal story where I  describe my experience with Rocky Mountain Spotted Fever or RMSF – a condition caused by Rickettsia rickettsii, a species of bacteria that is spread via tick bites. That blog post has become the most commented (178 so far) where people share with the world their horrifying accounts of RMSF.

There is a tool by Google – “Insights for Search” (still beta) that shows web search interest for a given search term(s) over a period of time. The results can be  filtered based on a geographical location, and general search categories. Google also offers an option to forecast the search trend for your query about one year into the future.

I examined the search phrase “rocky mountain spotted fever” in the US from 2004 to present. Here is the graph (click to enlarge):

Rocky Mountain Spotted Fever Search Trends (2004-2010)

As you can see, every year there is a significant spike in the number of searches around June; however, year after year that peak is becoming shorter and shorter, forming a steadily descending trend line.

What does this year over year decline imply? You could say if fewer people get sick, than less googling for “rocky mountain spotted fever” will be done, right? Well, I don’t think it is that simple. Google reliably shows that the interest is declining; however, you can still have a decline in interest while the number of people who get sick with RMSF holds steady or even increase. The explanation could be very simple – RMSF is easily misdiagnosed. When a doctor is presented with the initial onset of  symptoms such as high fever, muscle ache, headache, petechial rash and etc., I really doubt that Rocky Mountain Spotted Fever will even make the top 10 on the list.

The Center for Decease Control and Prevention (CDC) only shows the number of reported cases through 2002:

But as you can see there is a sharp increase in the number RMSF cases from 1997 to 2002, I seriously doubt that trend stopped, but I could be wrong.

The 2002 ANSI standard calls for effective radiation dose of 0.1 µSv or less per scan per person (interestingly, in 2009 ANSI relaxed that standard and increased the limit to 0.25 µSv). How much is 0.1 or even 0.25 µSv? Well, “Sv” stands for Sievert – a derived SI unit that measures biological absorption of ionizing radiation. The National Council on Radiation Protection and Measurements recommends the following annual radiation dose limit for an individual from all radiation sources other than natural background and the individual’s medical care is:

For members of the public who are exposed continuously or frequently, the recommended annual effective dose limit is 1 mSv (1000 µSv)

On an infrequent basis, a member of the public may receive more than 1 mSv (1000 µSv). In such a case, the annual effective dose may exceed 1 mSv up to a value of 5 mSv (5000 µSv)

* – the term “infrequent,” in the context used here, should refer to a justified exposure that is not likely to occur often in an individual’s lifetime, with each occurrence justified independently of any other.

As you can see, the Rapiscan Secure 1000‘s 0.1 µSv per person per scan radiation exposure is 10,000x lower than the maximum allowed annual limit.

However, Rez et al. in their recent article “The Dose From Compton Backscatter Screening” [1] estimate that the effective doses maybe be as high as 0.8 – 0.9 µSv which would be make it four times higher the allowed maximum 0.1 µSv per scan (with the assumption of two scans per passenger). The authors do point out that the increased doses to the passengers remains well below the exposure levels that are known to cause harm, but warn:

The major public health effect of concern at low doses of ionising radiation is cancer. There is clear evidence of cancer induction at effective dose above ~200 mSv. Below an effective dose of ~100 mSv radiogenic cancer mortality risk estimates for all cancers is highly uncertain. It is not possible to determine reliably whether a radiogenic risk is present in an X-ray screened population because of the high spontaneous incidence of cancer and the multifactorial nature of disease causation

Based on these findings I will probably have to permanently opt-out or go through L3′s millimeter wave RF machines. Since I was about 9 years old , I’ve been exposed to gamma rays from Cesium-137 (¹³⁷Cs) at 22 Ci/km² ( curies per square kilometer) . And don’t forget about radioiodine (Iodine-131 ¹³¹I), xenon and a bunch of other short half-life isotopes.  Can you guess where I grew up ? :)

References:

1.   Rez, P., Metzger, R. L. & Mossman, K. L. The Dose From Compton Backscatter Screening. Radiat Prot Dosimetry 1-7 (2010).

• Chapter 1  - monolithic columns (monolithic materials, pore formation,  near-IR,  chromatographic application)
• Chapter 3 – micro-HPLC (μHPLC systems, micro-columns, gradient elution)
• Chapter 4 – two-dimensional comprehensive LC
• Chapter 5 – gradient elution mode
• Chapter 6 – capillary electromigration techniques
• Chapter 8 – LC-MS Interfaces
• Chpater 16 – Polymer HPLC

Part II focuses on the four major practical applications of HPLC analysis:

• Chiral Pharmaceutical (method development using CSP and CMPA)
• Environmental
• Food
• Forensic Sciences (toxicology, explosives, dyes and ink, DNA analysis)

All chapters include extensive reference lists and summarizing tables.

Danilo Corradini (editor) and Terry M. Phillips (consulting editor) assert that “this edition is suitable as a textbook for undergraduate college students having a general background in chromatography and for new practitioners interested in improving their knowledge on the current status and future trends of HPLC“.

In light of the melamine crisis, the FDA increased sampling and analysis of imported milk-derived ingredients and products. Recently, the government also set a threshold of 1 µg/mL for melamine in infant formula, making it critical to have a low level melamine detection method. There are several analytical techniques that could be used to detect and quantify melamine:

Melamine Analytical Methods in Food Matrix

The HPLC-UV method has become the most popular method as the high cost of maintenance and operation of GC-MS, HPLC-MS and tandem mass spectrometry limit their practical use outside of specialized testing labs. However, the existing melamine HPLC methods require acetonitrile which has significantly increased in price due to the worldwide shortage caused by the global economic crisis. That’s where Venkatasami and Sowa (2010) come to the rescue. The scientists report the first known acetonitrile-free reverse-phase HPLC melamine detection method.

The analytical method uses 0.10% TFA/methanol (90:10) as the eluent and exhibits decent linearity (r>0.999) from 1.0 to 80 µg/mL with the limit of detection (LOD) 0.1 µg/mL and the limit of quantification (LOQ) 0.2 µg/mL.  The method’s analysis time of ~6 min per sample in acetonitrile-free mobile phase as well as its simplicity makes it very attractive for use in production facilites.

References:

• Mast, R. W., Jeffcoat, A. R., Sadler, B. M., Kraska, R. C., & Friedman, M. A. (1983). Metabolism, disposition and excretion of [14C]melamine in male fischer 344 rats. Food and Chemical Toxicology, 21(6), 807 – 810.
• World Health Organization (2009). Toxicological and health aspects of melamine and cyanuric acid. WHO library cataloguing-in-publication data (Report of a WHO Expert Meeting In collaboration with FAO). Geneva: World Health Organization. Retrieved November 26, 2010, from http://whqlibdoc.who.int/publications/2009/9789241597951_eng.pd
• Venkatasami, G. & Sowa, J. R. (2010). A rapid, acetonitrile-free, HPLC method for determination of melamine in infant formula. Anal Chim Acta, 665(2), 227-30.

While doing my “random” searches in Google Scholar I stumbled upon this article by Marc-David Munk – “Pine mouth” syndrome: cacogeusia following ingestion of pine nuts (genus: pinus). An emerging problem? “[1].  Incidentally, last year I did experience “pine mouth” syndrome and wrote about it in ”Cursed Pine Nuts or Triglycerides?“.

Dr. Munk  from Department of Emergency Medicine, University of New Mexico reported a case of metallogeusia (metallic taste) after a male patient ingested some pine nuts. The researcher documented the symptoms then conducted physical, dermatological, and dental examination of the patient followed by neurological, motor, sensory and reflex testing. All exams and tests came back normal and perceived cacogeusia improved without any treatment within 5 days (just like in my case).

Dr. Munk then put down his stethoscope, took off the lab coat, sat down in front of a computer and continued his research using “Google Trends”. He examined Google search volume for the terms “Pine Mouth”, “Pine Bitter” and “Pine Taste” over a period of time and noted a significant spike in search popularity in the 2nd quarter of 2009; however, Munk didn’t proceed any further to investigate the exact cause of the surge.

Unfortunately, Dr. Munk’s findings don’t provide the answer to a mechanism by which newly found triglycerides cause metallogeusia; however, he clearly shows that the correlation between pine nuts ingestion and metallic taste is real.

It’s been more than a year since I had a case of “pine mouth“, even though I have had plenty of pine nuts from various parts of the world: Russia, Italy and China. Could it be just an anomaly caused by some abnormal weather condition in China back in 2009 that caused pine trees to produce these unusual triglycerides?

Too bad I didn’t use the “pine mouth” term in my Aug 2009 blog post, otherwise, I might have made a reference in Dr. Munk’s article :-)

Reference:

[1] Munk, M. D. “Pine mouth” syndrome: cacogeusia following ingestion of pine nuts (genus: pinus). An emerging problem? J Med Toxicol 6, 158-159 (2010).

Upon arrival at SFO, I glanced at the security checkpoint and I saw a different type of body scanner – L3′s ProVision.  So it seems we have two competing advanced imaging technologies: OSI’s  backscatter X-Ray or so-called the Compton Scattering Effect and L3′s “active millimeter wave radio frequency” (MMW). Here is what each manufacture says about their product’s technology and safety:

OSI:

The Rapiscan Secure 1000’s patented technology is composed of an ultra low-dose X-ray source that images backscattered X-rays through to a remote operator’s workstation.

Emission Per Scan: Less than 10 microRem

L3:

Leveraging harmless radio waves, ProVision offers advanced imaging—without any health risks.
• The signals created by ProVision are 10,000 times lower than other commercial radio frequency devices.
• ProVision does not use X-rays or ionizing radiation.

Ok, it appears that OSI’s technology is patented and a quick search for all the US Patents assigned to “Rapiscan Systems, Inc” reveals 43 search results ( I used advanced “AN/Rapiscan” query in UPSTO Patent Full-Text and Image Database).

The very first patent 6,094,472 titled – “X-ray backscatter imaging system including moving body tracking assembly” was filed with the USPTO on 04/14/1998 by the inventor Dr. Steven W. Smith (Poway, CA).

As you can see from the  drawing above, it doesn’t quite look like a Rapiscan Secure 1000 system, however, the patent does provide some clues to a radiation exposure level:

“at least one X-ray source comprises an X-ray tube operating at a potential of 70 KV at 10 ma.”

“Radiation exposure is an important consideration in X-ray concealed object detection systems. The United States National Council on Radiation Protection (NCRP), in NCRP Report No. 91, “Recommendations on Limits for Exposure to Ionizing Radiation”, 1987, addresses this issue. In this report, the NCRP states that a radiation exposure of less than 1000 microRem per year in excess of environmental levels is negligible, and efforts are not warranted at reducing the level further. Persons employed in high security or secured facilities, or those who frequently travel by airlines, may be subjected to many hundred security examinations per year. A yearly radiation exposure limit of 1000 microRem permits a single scan exposure within the range of 1 to 10 microRem for the general public. In accordance with the NCRP recommendations, radiation levels significantly higher than this present a non-trivial health risk.”

“the scan duration for a complete scan is on the order of 0.3 seconds”

Alright, it looks like I can go through Rapiscan Secure about 100 times per year and I should be ok, right? But then I found this recent article published in “Radiation Protection Dosimetry” where Rez et el. [1] examine radiation exposure of Compton backscatter X-rays. The researches caution:

“Although vendor-determined doses are small and not associated with adverse health effects, dose accuracy is in question because of inherent difficulties in measuring X-ray exposures from rapidly moving X-ray beams.”

Hmm, it is getting interesting, I will continue dig dipper.

References:

[1] P. Rez, R.L. Metzger and K.L. Mossman, “THE DOSE FROM COMPTON BACKSCATTER SCREENING”, Radiat Prot Dosimetry, Nov. 2010.

Berezkin and Lapin conducted their experiments using HP 5890 gas chromatograph equipped with an electronic pressure control and a flame ionized detector (FID). The scientists used various length columns ranging from 0.1 to 5 meters to separate n-C9-n-C20 alkanes and showed that ultra-short columns were “good enough” for express-analysis of thermolabile and high-boiling compounds. The authors were optimistic of practical application of ultra-short capillary columns as an extension to conventional GC analysis.

[1] V. G. Berezkin, A. B. Lapin, Journal of Chromatography A 1075, 197 – 203 (2005).
[2] V. G. Berezkin, I. V. Malyukova, Zh. Anal. Khim. 52, 798 (1997) (in Russian).

The article hypothesizes that certain triglycerides, formed by unsaturated fatty acids, may attribute to the bitter taste; however, the role of these triglycerides remains a mystery. The good news is I should be able to taste food normally within a week or so.

I’ve eaten pine nuts in large quantities in the past but never experienced any taste problems, so perhaps it depends on the nuts’ origin.

According to the US Fire Administration, arson is the leading cause of fires and the second leading cause of deaths and injures, and that’s why arson investigation is of forensic significance for the criminal justice system.

Commercially available fuels or solvents that are mixtures consisting of hundreds of components are typically used to start a fire. Analysis becomes very difficult because ignitable liquids consist of same or similar components at different concentrations, in addition, fire may evaporate some of the components and thus altering the composition of residual ignitable liquids found in fire debris.

Gas chromatography – mass spectrometry (GC/MS) is a well established method for analysis of ignitable liquids; however, Yao Lu and Peter B. Harrington proposed a gas chromatography / differential mobility spectrometry (GC-DMS) method. The duo tested a variety of commercially available petroleum-based ignitable liquids and showed that two-way GC-DMS data provides more information for classification and better prediction results than either chromatograms or DMS spectra.

References: “Forensic Application of Gas Chromatography-Differential Mobility Spectrometry with Two-Way Classification of Ignitable Liquids from Fire Debris”, Yao Lu and Peter B. Harrington, Analytical Chemistry, 2007, DOI:10.1021/ac0707028

Zhaohui Wang and coauthors used a laser pulse to heat a gold substrate onto which a self-assembled monolayer of long-chain hydrocarbon molecules had been formed. The researchers used coherent vibrational spectroscopy to measure the heat conduction as it traveled through the chain of molecules via distinct vibrations. The heat flowed through the chains at about 1 kilometer per second in agreement with theoretical predictions.

_{References:
“Ultrafast Flash Thermal Conductance of Molecular Chains,” by Z. Wang, J.A. et al., Science, 317, pp 787-90, DOI:10.1126/science.1145220
“Molecules Take the Heat,” by A. Nitzan, Science, 317 pp.759-60, DOI: 10.1126/science.1147011}

Nano Liquid Chromatography

1. Nano Liquid Chromatography – Reloaded
2. Definition of Nano Liquid Chromatography
3. Columns in Nano LC
4. Nano LC Sensitivity

In theory, the analyte sensitivity increases on decreasing the column inner diameter; however, because of the very low sample volumes injected – 20-60 nL, nano liquid chromatography cannot be considered as an analytical method of high sensitivity.

There are several research studies that focused on the improvement of sensitivity by using techniques such as on-column focusing[1] and 2-D separation[2].

_{1. “Trace Level Determination of Organophosphorus Pesticides in Water with the New Direct-Electron Ionization LC/MS Interface”, Achille Cappiello et al., Analytical Chemistry, 2002 vol. 74 pp. 3547-54}

_{2. “Fully automated micro- and nanoscale one- or two-dimensional high-performance liquid chromatography system for liquid chromatography-mass spectrometry compatible with non-volatile salts for ion exchange chromatography” by Masuda, J. et al., Journal of Chromatography A 2005, 1063, pp. 57-69.}

The method uses a short column packed with 2.7μm “fused-core” silica particles that are made by fusing a 0.5μm layer of porous silica onto a solid silica particle[1]. These unique particles enable very rapid chromatographic separation at a relatively low backpressure.

Ultra-high-pressure liquid chromatography (UHPLC) is another chromatographic technique that allows the system to handle the high backpressure resulting from the stationary phase with sub-2μm particles. UHPLC offers advantages in chromatographic resolution, speed, and sensitivity over conventional HPLC systems.

Newly developed fast HPLC technology is comparable with UHPLC in terms of chromatographic performance but requires neither expensive ultra-high-pressure instrumentation nor new laboratory protocols.

_{1. “Fused-Core Silica Column High-Performance Liquid Chromatography/Tandem Mass Spectrometric Determination of Rimonabant in Mouse Plasma”, Yunsheng Hsieh et la., Analytical Chemistry, DOI: 10.1021/ac070343g}

EPA and DHA (docosahexaenoic acid) are the two main long-chain polyunsaturated fatty acids, also frequently referred to as “omega-3″. These lipids are primarily found in oily fish and shellfish. Some researches theorized that the consumption of the aquatic creatures and, hence, DHA/EPA is a key to the brain development of our prehistoric ancestors some 150,000 years ago^[2]. Omega-3s also have been found to reduce the risk of heart disease and stroke.

Chakraborty and Raj concentrated EPA from chemically hydrolyzed sardine oil using urea fractionation with methanol at different temperatures and urea/lipids ratios followed by argentation neutral alumina column chromatography. The urea-fatty acid complexes were analyzed by gas-liquid chromatography and gas chromatography-mass spectroscopy that revealed the highest EPA concentration of 48% was at 4 C and 4:1 urea/fatty acid ratio.

Lipid chemists heavily employ argentation chromatography – a technique that dependents on polar complexes that reversibly form between the silver ions and double bonds of the fatty acyl residues of lipids.

I get the science behind the silver ion chromatography, but what about the smell in the lab? You can only imaging that fish stench that permeates everything in its path and comes home with you on your clothes.

_{[1] “Eicosapentaenoic Acid Enrichment from Sardine Oil by Argentation Chromatography”, Kajal Chakraborty and R. Paul Raj J. Agric. Food Chem., ASAP Article DOI: 10.1021/jf071407r
[2] “The possible role of long-chain, omega-3 fatty acids in human brain phylogeny”, J G Chamberlain, Perspect Biol Med, 1996 vol. 39 pp. 436-45
“Evidence for the unique function of docosahexaenoic acid during the evolution of the modern hominid brain”, M A Crawford et la., Lipids, 1999 vol. 34 Suppl pp. S39-47}

The authors Eugene F. Barry (University of Massachusetts Lowell) and Robert L. Grob (Villanova University) discuss the development, performance, selection, and technology of columns for gas chromatography and include a handy list of packed column separations and guidelines for column selection in Appendices A and B. A subject index completes the book.

Book Description

Gas Chromatography (GC) is the most widely used method for separating and analyzing a wide variety of organic compounds and gases. There have been many recent advancements in both packed column and capillary column GC. With numerous options and considerations, selecting the right column can be complicated. This resource provides essential guidance for scientists and technicians, including:

• Methods of choosing both capillary and packed columns
• Selection of dimensions (column length, I.D., film thickness, etc.) and type of column
• Guidelines for proper connections of the column to the injector and detector
• United States Pharmacopeia and National Formulary chromatographic methods
• ASTM, EPA, NIOSH, and OSHA column selection specifications
• Information on the advantages of computer assistance in GC and multidimensional GC
• Comprehensive information on column oven temperature control

A single living cell is capable of performing a number of tasks: it can create a full copy of itself in less than an hour, sense its environment and respond to it, change its shape, and obtain energy from photosynthesis or metabolism, using principles that are similar to those of solar cells or batteries. And all this functionality comes from a variety of proteins.

In this Review authors focus on catalytic proteins that have moving parts, particularly kinesin and myosin proteins, that show a clear resemblance to machines. They found rotary motors with shaft and bearings and liner motors that move along filament tracks in a step-by-step motion powered by chemical energy derived from ATP or electric forces of ions.

One example is the bacterial flagellar motor used by bacteria such as E. coli as propulsion mechanism by spinning a helical flagellum. This powerful rotary biomotor made from more than 20 different proteins and generates torques of more than 1,000 pN-nm at 100 revolutions per second.

Currently there are some demonstrations of a biomolecular-powered nanostructures. A prominent example is the construction of a ~1 μm nickel nanopropeller rotated by F1-ATPase motor powered with ATP[1].

Although the latest advances in biomolecular motors in nanotechnology showed that the researches can use motor proteins to drive nanoscale components and interface proteins selectively to different materials, the authors note that many are still only at the proof-of-principle stage. And we are yet to witness a functional and useful device made from the biomolecular motors.

Yes there are challenges such as protein denaturation that limits the lifetime to several days but the small size and force-exerting of motor proteins and the range of potential applications gives them unique advantages over current human-made motors.

Upon studying and using biomotors, we will gather a lot of knowledge that is of interest to biology, material science, and chemistry, and it is reasonable to expect spin-offs for medicine, sensors, electronics, or engineering. And thus exploring biomotors in technology will remain an interdisciplinary playground for many years to come.

References: “Motor Proteins at Work for Nanotechnology,” by M.G.L. van den Heuvel and C. Dekker at Delft University of Technology in Delft, Netherlands, DOI: 10.1126/science.1139570

1. R. K. Soonget al., Science 290, 1555 (2000)

135th Birthday

1. Happy Birthday Professor Tsvet!
2. Chromatogram on the ceiling
3. Colorgram
4. From Switzerland to Russia
5. The Little Botanists

I am continuing the series dedicated to the chromatography‘s founder Mikhail Tsvet. So, in 1897 he moves to Russia from Switzerland, and here is his first impression of Russia:

“…during the first six months that I have been in Russia, in vain, I have been trying to force myself to feel that I have a Russian heart beating in my chest! I traveled throughout Russia. I visited Moscow, the holly city, and my eyes and ears were widely opened… Nothing moved, nothing responded in me. In my homeland I felt like a foreigner. And this feeling deeply and desperately is weighing on my mind… Now I regret that I left Europe…”

But later on the mood changed. Tsvet met with great people and prominent researches. Of great importance to him were the society meetings of “The Little Botanists”, that took place weekly in the homes of Beketov, Voronin or Famintsev’s lab. The meetings were held over dinner, in a relaxed atmosphere, and included discussions on science and a variety of other topics. The meeting also created that special climate, a peculiar state of mind that helped Tsvet to overcome “the cold of life”, and remained with him as the priceless memories.

However it was necessary to find a paying job. It turned out that Geneva University doctorate degree was not honored in Russia. It was not even equivalent to the Master’s degree. He spent many months searching for a job that sometimes felt like a hopeless case, and Tsvet was thinking about going to back to Europe. For teaching and, hence, an opportunity to do a scientific research, it was necessary to defend a new thesis in Russia.

Tsvet got extremely lucky. He got to know Petr Frantsevich Lesgraft – a great person, doctor, anatomist, and outstanding educator. Mikhail Semyonovich attended Lesgraft’s terrific lectures, and then continued the research of chloroplasts in the new biological laboratory specifically constructed for Lesgraft while preparing for exams and a thesis defense.

In 1899, he passed the finals, and on April 19th, 1900 Tsvet delivered a report entitled “The nature of chloroglobin” at the Botanist Section meeting of St. Petersburg Naturalist Society, and was accepted as a full member. On September 23rd, 1901 he defends a thesis with a title “The Physicochemical Structure of the Chlorophyll Grain” at Kazan University. Mikhail Tsvet’s life was starting to shape up…

Technorati Tags: Tsvet

Here is what I found based on the last 60 days of statistics:

1. People used 1966 various search terms
2. The top 20 keywords are:

Top 20

For example, someone searched for “principles of chromatography” and Yahoo! took him/her to my home page where I may have talked about “principles of chromatography” a month ago but this post is no longer on the front page.

Here is another one. The search term was “soy milk bad reactions” and Google presented the person with “Soy Milk, Good or Bad? HPLC vs CZE – Part 2” – the post about a study that compares HPLC and CZE methods for QC of soy beverages.

Alas, because of my choice of the words for the title, this post attracts visitors that google with the keywords such as “soy milk is it bad or good”, “soy milk bad”, “bad reaction from soy milk”, “soy milk versus cow milk”, “soy milk good vs bad”, “soy milk is it bad for health” and etc. Obviously, these poor souls won’t find the answers to their questions from my comparison of HPLC to CZE, sorry!

So I decided to go through some of the unanswered questions and answer them one post at time, so next time someone searches for “types of hplc detectors” they won’t be staring at the post on “Iodized Table Salt“.

The physical properties of the semiconductor materials in each cell allow one to absorb light at longer wavelengths and the other to absorb light at shorter wavelengths. Researchers have made tandem solar cells before, but the vapor-deposition methods used to produce the multilayer structure have made the cells relatively expensive.

Jin Young Kim and colleagues now describe a cheaper method for making a tandem semiconducting polymer cell, in which all of the layers, including the electrode connecting the two units, are processed from solution. They used bulk heterojunction materials made from semiconducting polymers and fullerene derivatives.

The cell’s efficiency exceeds 6 percent at illumination of 200 milliwatts per cm2, which is quite good for cells produced via an all-solution method.

Reference: “Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing,” by J.Y. Kim et al.
DOI: 10.1126/science.1141711

This spring I had become an avid admirer of the young asparagus shoots. And practically everyday for breakfast I had steamed or, sometimes, boiled organic asparagus served with cold pressed flaxseed oil and a little bit of soy sauce.

The taste was incredible, and I could never get enough of it. I even “promoted” asparagus to my second most favorite vegetable (after the fresh green peas, of course) but then came the smell…

It took me a few days to confirm the pattern:

asparagus for breakfast –> 15 – 20 min later –> a pungent odor of rotten cabbage in urine.

I immediately assumed that there is something wrong with my metabolism because when I questioned my friends they had no clue what I was talking about it. None one them smelled anything unusual in their urinary discharge after consuming asparagus.

I never got around to research my “problem” until yesterday when I was reading “Carbon Tet” blog and I saw Greg’s post about asparagus. Well, it turns out that I am ok. In fact, I am the lucky one who has the enzyme to break down asparagusic acid found in young asparagus plants.

The asparagus odor “problem” was first described by a Scottish mathematician and physician John Arbuthnot (1667-1735). In his book published in 1731 he wrote:

“asparagus… affects the urine with a foetid smell (especially if cut when they are white) and therefore have been suspected by some physicians as not friendly to the kidneys; when they are older, and begin to ramify, they lose this quality; but then they are not so agreeable”.

And since then more than a dozen of a research work was published on the subject.

Two of the studies conducted in 1956 and 1987 revealed that about 40-43% of the United Kingdom population produced the odor. Other similar studies were undertaken in Israel and China but concluded that all individuals excrete odorous urine following asparagus ingestion; however, these investigations have been subjective, the urine was smelled by individuals.

But in 1987 Waring and colleagues [1] examined the volatiles above urine samples. GC/MS (Gas Chromatography / Mass Spectrometry) identified six compounds above the “smelly” urine samples that were absent in the samples without the odor: methanethiol, dimethyl sulfide, dimethyl disulfide, bis(methylthio)methane, dimethyl sulfoxide, and dimethyl sulfone.

Out of these six, the most pungent compounds methanethiol (CH3-S-H) and dimethyl sulfide (CH3-S-CH3) probably give most of the odor, but the presents of bis(methylthio)methane (CH3-S-CH2-S-CH3) and methylsulfonylmethane (CH3)2SO2 could add sweet aroma.

Of the many sulfur-containing compounds found in asparagus only asparagusic acid (1,2-dithiolane-4-carboxylic acid) and its derivatives may be reduced in the body to its free thiol form, which could be methylated and then be a substrate for thionase-β-lyase activity liberating methanethiol.

Dimerization of methanethiol would yield dimethyl disulfide, while methylation and subsequent sulfur oxidation would give dimethyl sulfide, sulfoxide, and sulfone.

References:
1. “The chemical nature of the urinary odour produced by man after asparagus ingestion.”, Waring RH, Mitchell SC, Fenwick GR., Xenobiotica. 1987 Nov;17(11):1363-71.

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Tiny little devices traveling in our bloodstream while performing complete blood analysis and monitoring our well-being is the future of implantable biosensors. However, these nanorobots will need to be self-powered and there are two ways for achieving it – either to use a battery or to harvest energy from the environment.

Generating electricity “on-board” is a very attractive option for in vivo medical application because biological systems provide a great medium for converting chemical, thermal, or mechanical energy to electricity ensuring a lifetime operation.

Zhong Lin Wang and colleagues have developed a DC (direct-current) nanogenerator that converts mechanical energy into electricity. The basic principle is to use piezoelectric and semiconducting coupled nanowires (NWs), such as zinc oxide (ZnO). The nanogenerator used in the experiments was 2 mm2 and had a million of nanowires.

This nanogenerator has the potential of directly convert hydraulic energy in the human body, such as flow of body fluid, blood flow, heart beat, and contraction of blood vessels, into electric energy. But for now, a prototype of the nanogenerator is driven by ultrasonic waves through a metal frame suspended in air and creates a 25-35 nA current while submerged in 0.9% NaCl – a normal saline solution.

Reference: “Integrated Nanogenerators in Biofluid”, Nano Letters doi: 10.1021/nl0712567 S1530-6984(07)01256-8

Chemical reactions generally accelerate when temperature increase. However, in today’s issue of Science Magazine [1] a research group from France revealed a class of gas-phase reaction between oxygen atoms and alkenes that just do the opposite – the rate coefficients increase as the temperature is lowered.

Reactions of this sort may be taking place in interstellar clouds, which are difficult to study directly. Hassan Sabbah and colleagues have performed rate measurements between oxygen atoms and ethene, propene, 1-butene, cis-, trans-, and iso- butene over a range of temperatures from 20 to 300 Kelvin. Then they modeled the unusually rapid low-temperature rates, providing a theoretical framework for predicting reaction rates in systems that may be useful for understanding the chemistry of interstellar clouds.

1. “Understanding Reactivity at Very Low Temperatures: The Reactions of Oxygen Atoms with Alkenes”, doi:10.1126/science.1142373

In 2005, a group of researches from Italy analyzed water samples from the Po River in northern Italy for the presence of cocaine and its main urinary metabolite – benzoylecgonine (BE)[1]. They took samples each day for four different days and extracted cocaine and BE by solid-phase extraction followed by analysis on LC – MS/MS with electrospray ionization.

Though the concentrations of benzoylecgonine and cocaine in the river were small – 25 and 1.2 ng/L, it is equivalent to 4 kg of cocaine per day that flows down the river or 40,000 (!) doses per day based on a typical cocaine dose.

This year, Italian researches form the Institute for Atmospheric Pollution (IAP) theorized that if cocaine is in water, it could also be present in the air[2]. For example, cocaine seizures by the authorities and snorting can both release cocaine particles.

The group conducted a broad study of the composition of airborne particulates in Rome as well as the province of Taranto in southern Italy and the more remote location of Algiers.

Researches Angelo Cecinato and Catia Balducci from the IAP sampled inhalable air particles of diameter below 10 µm. The samples then undergone Soxhlet extraction followed by clean up on basic alumina column chromatography and analysis by Gas Chromatography Mass Spectrometry (GC/MS).

Cocaine was observed at detectable levels at all of the Roman locations including a university district, a city garden, a canyon street, a residential zone and a business district.

Airborne Cocaine Concentrations in Rome

1. University District – 98 pg/m3
2. City Garden – 70 pg/m3
3. Residential & Business areas – 12-21 pg/m3

In Taranto, samples were collected at three sites with following cocaine concentrations:

1. Downtown District – trace level
2. Rural Area – below LOQ (the quantification limit)
3. Residential Area – 10 pg/m3

The air particles collected around Algiers contained no cocaine above the detection limit.

Although the sources of cocaine in the air are not fully understood, the cocaine concentrations seemed to correlate with regional consumption of the drug in Rome and Taranto. By contrast, the concentrarion does not correlate with nicotine or caffeine, nor with benzo[a]pyrene.

1. “Cocaine in surface waters: a new evidence-based tool to monitor community drug abuse”
doi:10.1186/1476-069X-4-14

2. “Detection of cocaine in the airborne particles of the Italian cities Rome and Taranto”
doi:10.1002/jssc.200700039

Nano Liquid Chromatography

1. Nano Liquid Chromatography – Reloaded
2. Definition of Nano Liquid Chromatography
3. Columns in Nano LC
4. Nano LC Sensitivity

As I mentioned in the last post from this series, capillary columns of 10–100 μm inner diameter are commonly used in nano-liquid chromatography setups. They are typically made either from fused silica or PEEK materials currently found in your everyday Gas Chromatography or HPLC, respectively.

There are three basic types of capillary columns used in nano-liquid chromatography: packed, monolithic, and open tubular.

Packed Capillary Column
Packed columns are made by “stuffing” the capillary with silica-modified particles of 3–5 μm. Though recently, particles of even smaller sizes 1.5–1.8 μm were successfully employed in ultra performance LC (UPLC).

Such a small particle size provides nano-liquid chromatography systems with higher efficiency, resolution, selectivity, and shorter analysis time; however, it does increase the backpressure.

Due to the high cost and limited types of stationary phases available, many research labs pack the columns “in-house”. But it is a difficult and skill-demanding process. The trick is to make the particles of the same diameter and to avoid undesirable void volumes.

So far, the application of packed capillary columns is the most explored option in nano-liquid chromatography.

Monolithic Capillary Column
Monoliths are a block of continuous materials made of highly porous rods with two types of pore structures (macropores and mesopores of different sizes), which allow the use of higher flow rates and thus reduces the analysis time.

Monolithic polymer columns were first used in the late 1980s, but monolithic silica columns did not become commercially available until 2000. Presently four types of monolithic capillary columns can be found: particle fixed, silica based, polymer based, and molecular imprinted monolith.

Up-to-date there is not much research information on application of monolithic capillary in nano-LC.

Open Tubular (OT) Capillary Column
In open tubular liquid chromatography column, the capillary wall is coated with highly permeable porous material that serves as the stationary phase.

The OT capillary has lower sample loading capacity of the column, because only a small surface area is available for analyte interaction that can result in column overloading causing peak asymmetry and poor efficiency.

Two-thirds of U.S. oil consumption is used to meet transportation energy needs, so unless there is a way to safely and efficiently store hydrogen on board a vehicle, it will be impossible to make a step forward to a hydrogen based economy.

Hydrogen Storage Methods

Presently there are three major directions in research and development of hydrogen storage systems:

• Gaseous Hydrogen – storing hydrogen as a gas in tanks under high pressure. Recently 10,000-psi tanks made of lightweight carbon-fiber reinforced composites have been demonstrated and certified; however, the energy content of hydrogen at even at 10,000 psi is only 1/8th of gasoline at the same volume.

• Liquid Hydrogen – storage of liquid hydrogen in cryogenic containers offers a significant advantage: more hydrogen can be stored in a given volume as a liquid than can be stored in gaseous form. A major drawback of liquid storage is a lot of energy required for liquefaction, plus the loss of hydrogen due to evaporation.

• Solid-state – storing hydrogen in metal hydrides, in complex hydride materials, and in nanostructured materials. Researchers believe that metal hydrides may represent ideal storage systems. An example of metal hydride would be sodium borohydride (NaBH4) that by produces hydrogen while reacting with water:


NaBH4 + 2 H2O –> 4 H2 + NaBO2

Although there are more than 2,000 elements, compounds, and alloys that form hydrides, none of these materials has yet been demonstrated to meet all of the FreedomCAR targets set by the U.S. Department of Energy (see a table below).

Nanostructured Materials
_{A novel promising method for hydrogen storage.}

Since 1997, when it was reported that carbon nanotubes (CNTs) can store hydrogen, numerous experimental and theoretical works have been performed in order to investigate the hydrogen adsorption in CNTs and improve the storage capacity of the tubes by doping them with alkali metals such as lithium and potassium. But most of these efforts failed to reach the year 2010 target of 6 wt % as set by the FreedomCAR.

One novel material that could be promising for H2 storage is the carbon nanoscroll (CNS). This carbon material shows a spiral form and can be obtained by a twisting of a graphite sheet. The researches from Greece implemented a multiscale theoretical approach to investigate the hydrogen storage in CNSs (DOI:10.1021/nl070530u).

Initially the researches failed to show any positive results because the intralayer distance of CNSs was too small to insert molecular hydrogen. Then they tried to open the spirals by inserting various alkali metals – Li, Na, K, and Rb, and only in case of Rubidium that opened the structure to 6.2 Å there was some adsorption of hydrogen.

Froudakis and colleagues determined that by opening the spiral structure even more to approximately 7 Å followed by alkali doping can make CNSs very promising materials for hydrogen storage application, reaching 3 wt % at ambient temperature and pressure.

FreedomCAR Hydrogen Storage System Targets