Study On Microstructure And Thermal Stability Of Natural Leather

The thermal stability is an important factor in the wear performance of leather. In theearly stage of literature searching, we found much of the researches about this property arebased on macroscopical experiment methods at present, there is no microscopic analysis ofleather thermal stability. In this study, through the method of molecular dynamics simulations,we further understand the internal structure of typeⅠcollagen molecules, which is the maintype protein molecules of natural leather. This research through establishing molecularmodels of natural leather and analysising conformation of the simulated trajectories toidentify the relationship between the thermal stability of natural leather and its internal spaceconformation.We first download ID for 1cgd of typeⅠcollagen from protein database, which is thebasic material of natural leather. Then using molecual dynamics simulation method throughthe TINKER software to 1cgd in Amber 99 force field and free boundary conditions, for the3176 steps energy optimization by using conjugagradient method. Third, using the canonicalensemble, Beeman algorithm, and time step of 1 fly seconds, for molecular dynamicssimulation with 1 ns respectively at 260 K, 300 K, 340 K and 380 K. Finally we successfulestablished typeⅠcollagen molecular model of 1 cgd at different temperatures.At last we analyze the simulated trajectories under different temperatures by these threeparameters, the root mean square deviation, radius of gyration and hydrogen bonding, as wellas the trajectories at different moments intercepted by the Force Field Explorer software. Theresults of typeⅠcollagen conformation as the temperature changes contain four aspects. First,when the temperature rise, the value of root mean square deviation increases from 1 to 5 ,typeⅠcollagen space conformation deviates from the natural conformation increasely, thestability decreased. Second, when the value of radius of gyration decreases from 25 to22.5 as the temperature rise, typeⅠcollagen protein structure becomes more closely. Third,the numbers of intramolecular hydrogen bond of typeⅠcollagen molecules decrease from 955to 735, which is the reason for the stability decline. Last, There are three main types ofhydrogen bonds to stabilize the typeⅠcollagen, the formation of hydrogen bonds between theNo. 6 in the A chain of glycine and No. 4 in the C chain of proline, between proline in the 7thof B chain and hydroxyproline in the 5th of A chain, in addition, between proline in the 4th ofA chain and hydroxyproline in the 5th of C chain.