Author
 |
Ralston, Nicholas |
|
Hunt, Curtiss |
|
Submitted to: Biochimica et Biophysica Acta
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/8/2001 Publication Date: 7/1/2001 Citation: Ralston, N.V.C., Hunt, C. 2001. Diadenosine phosphates and S-adenosylmethionine: novel boron binding biomolecules detected by capillary electrophoresis. Biochimica et Biophysica Acta. 1527:20-30. Interpretive Summary: Boron is an element naturally present in soil and water and therefore present in plants and animals. We know that plants need boron to survive and grow and there is new evidence that animals and humans also need boron. It has been very difficult to determine how plants, animals, and humans use boron because it is very hard to detect when boron is attached to molecules. However, we recognized that boron gives an electric charge to molecules after it attaches to them. We used a new type of instrument that is sensitive enough to detect this charge and discovered a way to distinguish molecules that attach to boron from those that do not. This accomplishment is important because molecules that need boron to function in the body cannot otherwise be identified in the presence of other molecules in blood and body tissues. We used our method to study various molecules with specific components that enable them to attach to boron, and as we predicted, molecules with two of these components were better at holding onto boron. While developing our method we discovered four molecules that have much greater attraction for boron than any previously known molecules present in humans and animals. Three of these molecules are of a recently discovered type with many functions including control of blood clotting. The fourth is significant in many basic biologic processes and may be used to prevent or treat arthritis, depression, and liver disease. Our results suggest these molecules may need boron to perform their normal functions. Our new method can now be used to examine blood and body tissues to look for other molecules that need boron to function normally. This information will help us learn how the body uses boron in the diet to prevent disease and promote health. Technical Abstract: There is emerging evidence that boron may have a physiological function in animals and humans but the search for high affinity boron binding species has been difficult because useful radioactive boron isotopes do not exist. In capillary electrophoresis (CE), the migration time of a ligand is increased in proportion to boron residence in the binding site. We exploited this phenomenon to detect boron binding and examine how molecular structure and proximal electronic charge influences the boron affinity of biomolecules. We found that the boron affinity of selected biomolecules varied widely with S-adenosylmethionine (SAM) and various di- adenosine polyphosphates (ApnA) exhibiting the highest affinities for boron: SAMAp6AAp5A>Ap4A>Ap3ANAD+>Ap2A>NADH5'ATP>5'ADP> 5'AMP>adenosine>3'AMP2'AMPcAMPadenine. Test species with vicinal cis- diols exhibited increased migration times in the presence of boron; species without those moieties did not. The cationic sulfonium present in SAM apparently greatly enhanced boron binding. In the ApnA species, cooperative complexing of boron apparently occurred between the two terminal ribose moieties because boron affinity increased as more phosphate groups (beyond three) were placed between those moieties. The CE method we developed and used allowed discovery of important biomolecules present in animal tissues, Ap6A, Ap5A, Ap4A, and SAM, that have higher affinities for boron than any other currently recognized boron ligand including NAD*+. |
