Cooperative hydrogen-bonding in models of self-assembled peptide nanomaterials.
Item
-
Title
-
Cooperative hydrogen-bonding in models of self-assembled peptide nanomaterials.
-
Identifier
-
AAI3292489
-
identifier
-
3292489
-
Creator
-
Chen, Yung-fou.
-
Contributor
-
Adviser: Joseph J. Dannenberg
-
Date
-
2007
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Chemistry, Physical
-
Abstract
-
The effects of H-bond cooperativity of various peptide structures (glycine, diglycine and their derivatives) and various H-bond donor-accepter sequences are investigated by ab initio calculations. Frequency analysis of the C=O coupling effects due to H-bond cooperativity on infrared (IR) spectra of 4-pyridone and various diglycine derivatives inserted with acetylene spacers are also performed. The H-bond interactions of carboxylic acids and amides dimers, the mixed dimers, and dimers can be manipulated by alkyl substitutions. The strengths of individual N-H···O and O-H···O H-bonds show significant variations in different structures. However, one should consider not only the strength of interactions but also the possibilities to further expand the structures in designing structures.;The influences of H-bond donor and acceptor sequences and the insertion of several spacers, such as acetylene and benzene are of interest. I investigated the groups of the DA-DA, DA-AD and AD-DA sequences. The results show the H-bond interactions are stronger when the dipole moments are aligned in opposite directions in those structures.;That the range of enthalpies for N-H···O H-bonds can vary from as little as 2 to as much 23 kcal/mol depends primarily upon the polarizability of whatever internally connects the N-H and C=O within the H-bonding molecule, which are two parallel -C=C entities in 4-pyridone. The contribution of covalent or charge-transfer interactions between the pi-systems of adjacent 4-pyridones is small.;The C=O and N-H coupling in H-bonded chains of 4-pyridones was also studied. 14C-substitutions are used to decouple various vibrations for purposes of illustration. The coupling of the C=O's occurs primarily via the cooperative H-bonds rather than transition dipole coupling (TDC) as demonstrated by (1) the fact that the couplings are greater than previously reported for similar studies on formamides despite the greater distance between the C=O's in the pyridone chains; and (2) the red shifts can be attributed to the changes in the geometries (particularly the C=O bond lengths) of the individual 4-pyridones in the H-bonding chains induced by the H-bonds resulting polarization of the monomers.
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
