• Journal of the Korean Chemical Society
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• v.58 no.6
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• pp.560-568
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• 2014

The contribution of electrostatic interactions to protein folding reaction was studied by using mutant ubiquitin with lysine to alanine mutation at residue position 29. Based on the three dimensional structure of ubiquitin, lysine 29 is located close to negatively charged glutamate 16 and aspartate 21 and considered to stabilize the native state of ubiquitin by electrostatic interactions between these residues. The equilibrium unfolding experiment showed that the native stability was decreased by about ~20% upon mutation. This observation indicates lysine 29 indeed forms electrostatic interactions with nearby residues. Folding kinetics measurements using stopped-flow device and quantitative analysis of kinetics data indicate that ubiquitin folds from unfolded state to native state via intermediate state as observed previously. This intermediate state was observed to form immediately after the initiation of folding reaction. The folding intermediate was shown to be destabilized considerably upon lysine to alanine mutation. These observations indicate that electrostatic interactions can form early stage of protein folding and hence lead the folding reaction.

• Polymer(Korea)
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• v.24 no.2
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• pp.201-210
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• 2000

To determine the effect of chain length of linear amine curing agents on the thermal and mechanical properties, standard epoxy resin, diglycidyl ether of bisphenol A (DGEBA) was cured with diethylenetriamine (DETA), triethylenetetraamine (TETA) and tetraethylenepentaamine (TEPA) in a stoichiometrically equivalent ratio. From this work, the effect of linear amine curing agents on the thermal and mechanical properties was significantly influenced by chain length of curing agents. In contrast, the results showed that the DGEBA/DETA system had higher values than the DGEBA/TETA and DGEBA/TEPA system in the density, shrinkage (%), thermal expansion coefficient, tensile modulus, and flexural strength. Whereas the DGEBA/DETA cure system had lower values than the DGEBA/TETA and DGEBA/TEPA cure system in the maximum exothermic temperature, conversion (%), and T$_{g}$. These findings imply that the differences in the maximum conversion about the chain length of curing agents affect the thermal and mechanical properties.s.

• Journal of the Korean Chemical Society
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• v.47 no.2
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• pp.104-108
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• 2003

The reaction of $[Cu(L)]Cl_2{\cdot}H_2O(L=3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^{1.18},0^{7.12}]docosane)$ with 2,5-pyridinedicarboxylate(pdc) led to the formation of $[Cu(L)(H_2O)](pdc){\cdot}6H_2O(1)$. The structure was characterized by X-ray crystallography and spectroscopic method. The coordination geometry around the copper atom is a distorted square-pyramid with four secondary amines of the macrocycle occupying the basal sites and a water molecule at the axial position. Intermolecular hydrogen bonds in 1 form a three-dimensional molecular network.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.990-995
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• 1999

To determine the effect of chemical structure of linear amine curing agents on thermal and mechanical properties, standard epoxy resin DGEBA was cured with ethylene diamine(EDA) and hexamethylene diamine(HMDA) in a stoichiometrically equivalent ratio. From this work, the effect of linear amine curing agents on the thermal and mechanical properties is significantly influenced by the chemical structure or chain length of curing agents. In contrast, the results show that the DGEBA/EDA system having the two carbons had higher values in the thermal stability, maximum conversion of epoxide, density, glass transition temperature, tensile modulus, flexural strength, and flexural modulus than the DGEBA/HMDA system having the six carbons, whereas the DGEBA/EDA cure system had relatively low values in the shrinkage(%), thermal expansion coefficient, tensile strength, and had similar values in the maximum exothermic temperature, and conversion of epoxide compared to the DGEBA/HMDA cure system. This findings indicate that packing ability in the HMDA structure affects the thermal and mechanical properties.