Protein H-bonds

Ramachandran s stereochemical plot diagram) of dipeptides has been widely used to predict the secondary structures of proteins [306-309]. It is well known that the calculations on the polypeptides are limited by the number of atoms and hence high level ab initio and DFT calculations have been possible recently only. Several theoretical calculations with different levels of accuracy have been made on the polypeptides to study the < )- 1> plot distribution, H-bonding interactions, and stability [1-4, 308-322]. In the stability of polypeptides and proteins, H-bond plays an important role in the formation of the secondary structures such as the a-helix, (3-sheet, etc., and higher-order structures [1-4]. Quantum chemical calculations on some of the secondary structures in peptides and proteins ((3-sheets, (3-turns, and y-turns) at the HF and MP2 levels have been performed with special emphasis to the H-bonded structures... 

H-bonds between sugar-phosphate backbone and protein help anchor protein to DNA... 

The secondary structures we have described here are all found commonly in proteins in nature. In fact, it is hard to find proteins that do not contain one or more of these structures. The energetic (mostly H-bond) stabilization afforded by a-helices, /3-pleated sheets, and /3-turns is important to proteins, and they seize the opportunity to form such structures wherever possible. 

Why should the cores of most globular and membrane proteins consist almost entirely of a-helices and /3-sheets The reason is that the highly polar N—H and C=0 moieties of the peptide backbone must be neutralized in the hydrophobic core of the protein. The extensively H-bonded nature of a-helices and /3-sheets is ideal for this purpose, and these structures effectively stabilize the polar groups of the peptide backbone in the protein core. 

H bonding also vitally influences the conformation and detailed structure of the polypeptide chains of protein molecules and the complementary intertwined polynucleotide chains which form the double helix in nucleic acids.Thus, proteins are built up from polypeptide chains of the type shown at the top of the next column. 

Chen et al. utUized a direct chemical reaction with a given solution (wet treatment) to modify the surface of the silicone rubber. The presence of a layer of PEO on a biomaterial surface is accompanied by reductions in protein adsorption, and cell and bacterial adhesion. In order to obtain a PEO layer on top of the silicone rabber surface, the surface was firstly modihed by incorporating an Si-H bond using (MeHSiO) , and followed by PEO grafting to the surface using a platinum-catalyzed hydrosilylation reaction. These PEO-modified surfaces were demonstrated by fibrinogen adsorption both from buffer and plasma, as well as albumin adsorption from buffer. Reductions in protein adsorption of as much as 90% were noted on these surfaces. 

Mosmann TR, Cherwinski H, Bond MW. Giedlin MA, Coffman RL Two types of murine helper T cell clone. I. Definition according to profiles of lym-phokine activities and secreted proteins. J Immunol 1986 136 2348-2357. 

When they are protonated, amines are compatible with water, a property critical in biochemical processes because it helps biological macromolecules dissolve in water. The N—H bond in an amine is fairly easy to break, so amines participate in the formation of several important classes of polymers, including nylon and proteins. 

The secondary structure of a protein is determined by hydrogen bonding between CDO and N—H groups of the peptide linkages that make up the backbone of the protein. Hydrogen bonds can exist within the same protein... 

Recently it has been found that couplings between and C across H-bonds, e.g. in systems containing N—H..-0= C units (in proteins), can be directly detected and provide evidence for H-bonds in proteins and nucleic acids [89]. Although this technology is now standard for larger biomolecules it is rarely used for smaller molecules [90]. 

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