No abstract

No abstract

No abstract

No abstract

SynopsisThe proton magnetic resonance spectrum of thyrotropin releasing factor (TRF) in solution in deuterium oxide and deuterated dimethylsulfoxide (DMSO-d6) has been analyzed. Two forms differing in cis-trans isomerism about the His-Pro peptide bond are observed. From the temperature dependence of chemical shift of the amide protons, it is concluded that TRF in DMSO-d6 does not contain intramolecular hydrogen bonds. Measurement of NH-C,H coupling constant provides an estimate of the histidine dihedral angle 4. Structural information about the histidine sidechain is deduced frcm C,H-CpH coupling constants and from the nonequivalence of the two prolyl &-protons. In DMSO-ds, there is evidence for a tautomeric equilibrium corresponding to an exchange of imidazole proton between the two nitrogen atoms N-6 and N-E. In water, the N-EH tautomer is found to be the predominant tautomeric form of the imidazole ring. These resultd in combination with energy calculation, vibrational analysis, and carbon nmr studies allow the determination of the conformation of TRF.

No abstract

SUMMARY The replicas obtained from various microemulsions prepared under different freezing conditions were observed by electron microscopy. The difficulties encountered in obtaining proper freezing may be related to the peculiar properties of such systems. A proposal is made for using systems with particular physical characteristics, which preserve the micellar structure during freezing, instead of looking for perfect freezing conditions. This proposal proved to be successful.

No abstract