Vitamins doing gymnastics: Scientists capture first full image of vitamin B12 in action

But when it gets inside your body, new research suggests, B12 turns into a gymnast.

In a paper published recently in the journal Nature, scientists from the University of Michigan Health System and the Massachusetts Institute of Technology report they have created the first full 3-D images of B12 and its partner molecules twisting and contorting as part of a crucial reaction called methyltransfer.

That reaction is vital both in the cells of the human body and, in a slightly different way, in the cells of bacteria that consume carbon dioxide and carbon monoxide. That includes bacteria that live in the guts of humans, cows and other animals, and help with digestion. The new research was done using B12 complexes from another type of carbon dioxide-munching bacteria found in the murky bottoms of ponds.

The 3-D images produced by the team show for the first time the intricate molecular juggling needed for B12 to serve its biologically essential function. They reveal a multi-stage process involving what the researchers call an elaborate protein framework – a surprisingly complicated mechanism for such a critical reaction.

U-M Medical School professor and co-author Stephen Ragsdale, Ph.D., notes that this transfer reaction is important to understand because of its importance to human health. It also has potential implications for the development of new fuels that might become alternative renewable energy sources.

"Without this transfer of single carbon units involving B12, and its partner B9 (otherwise known as folic acid), heart disease and birth defects might be far more common," explains Ragsdale, a professor of biological chemistry. "Similarly, the bacteria that rely on this reaction would be unable to consume carbon dioxide or carbon monoxide to stay alive – and to remove gas from our guts or our atmosphere. So it's important on many levels."

In such bacteria, called anaerobes, the reaction is part of a larger process called the Wood-Ljungdahl pathway. It's what enables the organisms to live off of carbon monoxide, a gas that is toxic to other living things, and carbon dioxide, which is a greenhouse gas directly linked to climate change. Ragsdale notes that industry is currently looking at harnessing the Wood-Ljungdahl pathway to help generate liquid fuels and chemicals.

In addition to his Medical School post, Ragsdale is a member of the faculty of the U-M Energy Institute.

In the images created by the team, the scientists show how the complex of molecules contorts into multiple conformations -- first to activate, then to protect, and then to perform catalysis on the B12 molecule. They had isolated the complex from Moorella thermoacetica bacteria, which are used as models for studying this type of reaction.

The images were produced by aiming intense beams of X-rays at crystallized forms of the protein complex and painstakingly determining the position of every atom inside.

"This paper provides an understanding of the remarkable conformational movements that occur during one of the key steps in this microbial process, the step that involves the generation of the first in a series of organometallic intermediates that lead to the production of the key metabolic intermediate, acetyl-CoA," the authors note.

Senior author Catherine L. Drennan from MIT and the Howard Hughes Medical Institute, who received her Ph.D. at the U-M Medical School, adds, "We expected that this methyl-handoff between B vitamins must involve some type of conformational change, but the dramatic rearrangements that we have observed surprised even us."

More information: Nature, doi:10.1038/nature10916

Provided by University of Michigan (news : web)

Better analysis methods for vitamin D

As featured in a three-part series in the March 2012 issue of Agricultural Research magazine, the Beltsville center's Food Composition and Methods Development Laboratory is using new spectrometry methods to discover compounds in foods that have never before been documented.

Accurate data on the amount of vitamins and minerals in the U.S. food supply is critical to accurately assessing the intakes of these nutrients in the U.S. population. At the Beltsville center, chemist Craig Byrdwell has pioneered new, highly precise methods for analyzing vitamin D in foods and dietary supplements.

Byrdwell found that there are many ways in which multiple instruments that measure molecules can be used in parallel to provide much more information about food samples than single instruments used alone. These molecular mass-measuring instruments are called "mass spectrometers." One of Byrdwell's techniques is "triple-parallel mass spectrometry," in which three mass spectrometers, operating in different modes, are used in parallel.

Byrdwell's experiments also have shown that two systems for separating molecules (liquid chromatographs) can be used in combination to analyze complex food samples for vitamin D and its metabolites. Byrdwell authored a book chapter describing his vitamin D analysis methods, which appears in Extreme Chromatography, published by AOCS Press in Champaign, Ill. Byrdwell is also a coeditor of the book, which was published in May 2011.

Read more about the ARS national program for human nutrition monitoring in Agricultural Research magazine's March 2012 issue.

Provided by USDA Agricultural Research Service

New standard for vitamin D testing to ensure accurate test results

Karen Phinney and colleagues explain that medical research suggests vitamin D deficiency or insufficiency may be even more common than previously thought and a risk factor for more than just bone diseases. An estimated 50-75 percent of people in the U.S. may not have enough vitamin D in their bodies. Low levels of vitamin D have been linked to the development of several conditions, including rickets (soft and deformed bones), osteoporosis, some cancers, multiple sclerosis and Parkinson's disease. People can make their own vitamin D simply by rolling up their shirt sleeves and exposing their skin to sunlight. But for those cooped up in offices all day long, food and dietary supplements also can provide vitamin D. With this renewed interest in vitamin D, scientists need an accurate way to measure its levels in the blood. Measuring vitamin D itself doesn't work because it is rapidly changed into another form in the liver. That's why current methods detect levels of a vitamin D metabolite called 25(OH)D. However, the test methods don't always agree and produce different results. To help laboratories come up with consistent and accurate methods, the researchers developed a Standard Reference Material called SRM 972, the first certified reference material for the determination of the metabolite in human serum (a component of blood).

The researchers developed four versions of the standard, with different levels of the vitamin D metabolites 25(OH)D2 and 25(OH)D3 in human serum. They also determined the levels of 3-epi-25(OH)D in the adult human serum samples. Surprisingly, they found that this metabolite — previously thought to only exist in the blood of infants — was present in adult serum. "This reference material provides a mechanism to ensure measurement accuracy and comparability and represents a first step toward standardization of 25(OH)D measurements," say the researchers.

More information: Development and Certification of a Standard Reference Material for Vitamin D Metabolites in Human Serum, Anal. Chem., 2012, 84 (2), pp 956–962. DOI: 10.1021/ac202047n

Abstract
The National Institute of Standards and Technology (NIST), in collaboration with the National Institutes of Health’s Office of Dietary Supplements (NIH-ODS), has developed a Standard Reference Material (SRM) for the determination of 25-hydroxyvitamin D [25(OH)D] in serum. SRM 972 Vitamin D in Human Serum consists of four serum pools with different levels of vitamin D metabolites and has certified and reference values for 25(OH)D2, 25(OH)D3, and 3-epi-25(OH)D3. Value assignment of this SRM was accomplished using a combination of three isotope-dilution mass spectrometry approaches, with measurements performed at NIST and at the Centers for Disease Control and Prevention (CDC). Chromatographic resolution of the 3-epimer of 25(OH)D3 proved to be essential for accurate determination of the metabolites.

Provided by American Chemical Society (news : web)