科研之友
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摘要
The role of formaldehyde (HCHO) in vegetable-aldehydecollagen cross-linking reaction was investigated at the B3LYP/6-31 G(d) level, where lysine (LYS) was used as model of collagen and catechin (EC) as model of condensed vegetable tannin. Atomic charge and Frontier molecular orbital analysis show that intermediates formed by HCHO reacting with LYS or EC, that is, MLYS, MEC-6, and MEC-8, still have both nucleophilic and electrophilic sites, which are elements to form ternary cross-linking in vegetable-aldehydecollagen system. The analysis of energy gap between HOMO (highest occupied molecular orbit) and LUMO (lowest unoccupied molecular orbit) indicate that the intermediate of HCHOLYS residues (MLYS) can further react with free HCHO to form product P-N(CH2OH)2 (P-N-represents amino acid residue; N represents nitrogen atom on side chain), but the reaction of intermediate MLYS with free EC is difficult to take place. So, the probability of forming ternary cross-linking structure of amino acid residueHCHOEC is small, if HCHO is added before vegetable tannin in vegetable-aldehydecollagen system. However, the reactions of ECHCHO intermediates (MEC-6 and MEC-8) with free amino acids, HCHOamino acid residue intermediate (MLYS), as well as with other ECHCHO intermediates (MEC-6 and MEC-8), are very easy to take place. The reaction enthalpy also shows that the cross-linking tendency is favorable in thermodynamics. So, it can be deduced that covalent cross-linking among amino side chain of collagen and vegetable tannin may take place when aldehyde is added after vegetable tannin. In this way, a multiple point cross-linking reaction occurs to create a high stabilization of collagen.
- 出版日期2012-8-15
- 单位四川大学
