Abstract: The stories about scientists and their findings were itroduced as episodes in biological chemistry classes. The instructional effect on the motivation of students was examined. The results of questionaire answered by the students showed that they want to listen to the episodes and increase their their knowledge much more. The two better opportunities to tell episodes were at the beginning of the lecture and at the end of each topic indluded in the lecture. Fine episode introduction wiould make the motivation of students strong and the knowledge widespread.
Abstract: Living organisms have one-handed structures of L-amino acids in proteins and D-sugars in nucleic acids. Although the origins of each one-handed structure (or homochirality) have been discussed for many years, these discussions have been restricted to monomeric compounds, such as amino acids and monosaccharides, or their stereospecific condensation reactions. Oligomers of these compounds have to be considered in the accumulation processes of homochirality because of the differences in physical properties of the diastereomers. High-performance liquid chromatography (HPLC) and the calculation of the partition coefficient values showed that the peptides having heterochiral sequences like L-Ala-D-Ala or D-Ala-L-Ala were more hydrophobic than the peptides having homochiral ones (L-Ala-L-Ala and D-Ala-D-Ala). Similar results were given from the calculation of most linear dipeptides and all cyclic ones composed of Gly, Ala, Val, or Asp. In addition, longer homo-oligopeptides composed of Ala, Val, or Asp also gave similar results. This general tendency would be useful for the separation of diastereomeric oligopeptides in water. The results also suggest that the separation of the homochiral peptides from the heterochiral ones by their solubility in water could have progressed in a primitive hydrosphere.
Abstract: The presence of N-methyl-D-glutamate (NMDG) and N-methyl-L-glutamate (NMLG) has been demonstrated in the tissues of Scapharca broughtonii, which are known to contain N-methyl-D-aspartate (NMDA). To our knowledge, this is the first report on the natural occurrence of NMDG and the occurrence of NMLG in eukaryotes. These compounds were identified according to the following findings; (a) their derivatives with (+)- and (-)-l-(9-fluorenyl)ethyl chloroformate (FLEC) showed identical behaviors with those of authentic NMDG and NMLA, respectively, on high-performance liquid chromatography (HPLC), (b) the HPLC peak of NMDG disappeared when the extract, as well as the authentic compound, was treated with D-aspartate oxidase before derivatization, (c) they behaved identically with authentic compounds on thin-layer chromatography and differently from NMDA. Both or either of NMDG and NMLG were also detected in several mollusks and other animals. Concentrations of the enantiomers were comparable in the tissues of S. broughtonii and a few other species.
Abstract: A series of C-terminal deleted analogs of human growth hormone-releasing factor (hGRF) with either an amidated or a free carboxylic acid C-terminus were synthesized by solid phase methodology. Their capacity to release growth hormone was tested on rat anterior pituitary cells in monolayer culture. A gradual decrease of bioactivity down to 23% relative to hGRF was noted when the C-terminal amino acids were deleted to hGRF (1-34)OH. Further deletions, however, did not decrease the bioactivity because the potencies of the fragments, hGRF(1-31)NH2, (1-30)NH2 and (1-29)NH2 remained at about 50% of that of hGRF. Continual deletion of residues to hGRF(1-23)NH2, (1-22)NH2 and (1-21)NH2 still yielded bioactive fragments with full intrinsic activity despite very low potency. Only with the deletion down to hGRF(1-19)NH2 did the bioactivity completely disappear. Thus, together with the data published in a previous paper (1), the minimal biologically active core of hGRF with full intrinsic activity comprises the fragment (3-21).
Abstract: Eight position-1 analogs of the 40-amino acid fragment and two position-1 analogs of human growth hormone-releasing factor were synthesized by solid phase methodology and their capacity to release growth hormone was determined using rat anterior pituitary cells in monolayer culture. Relative to hGRF(1-40)OH, which was arbitrarily assigned a potency value of 1, [D-Tyr1]hGRF(1-40)OH, [Phe1]hGRF(1-40)OH, [Trp1]hGRF(1-40)OH, [His1]hGRF(1-40)OH, [Ala1]hGRF(1-40)OH, [(-Ac)Tyr1]hGRF(1-40)OH, Arg0-hGRF(1-40)OH and Ala0-hGRF(1-40)OH have potencies of 0.022, 0.038, 0.003, 0.351, 0.010, 0.032, 0.002 and 0.007 respectively. Relative to hGRF(1-44)NH2 = 1, [(3-Me)His1]hGRF(1-44)NH2 and [(O-Me)Tyr1]hGRF(1-44)NH2 have potencies of 0.132 and 0.001 respectively. These results demonstrate the prerequisite for an aromatic residue at position-1 for potent biological activity and also suggest that the capacity for hydrogen bond formation with the first residue is required for full receptor-ligand interaction.
