ABSTRACT
The effect of some organic compounds on the corrosion corr behavior of copper - iron alloy [1] and copper - aluminium - iron alloy [II] in 0.5 M H[2]SO[4] aqueous solution was investigated. The techniques of measurements were: weight loss, linear polarization and impedance spectroscopy. The organic compounds were: glycine [I], alanine [II], valine [III], histidine [IV], 2- aminothiazole [V] and 3- methyl -1- phenyl -2- pyrazolin -5- one [VI]. These compounds have high inhibition efficiency increases according to the order: I < II < III < IV < VI < V. The inhibitory effect of these compounds is achieved by their adsorption on the metallic surface via adsorption centers [N - atom and / or S- atom]. Their adsorption the metallic surface follows Temkins' isotherm of adsorption. The values of standard free energy of adsorption, delta G[degree sign] [ads], were calculated from the adsorption isotherms. The negative values of delta G[degree sign] [ads] indicate the adsorption process occurs spontaneously. There is an agreement between the results obtained from the different techniques of measurements
Subject(s)
Corrosion , Sulfuric Acids , Glycine/chemistry , Alanine/chemistry , Valine/chemistryABSTRACT
Firstly, parathyroid hormone (1-14) [PTH (1-14)] analogue containing various alpha-amino-iso-butyric acid residue (Aib) was synthesized by exchanging the 1st and 3rd Ala residues of alpha carbon of PTH (1-14). This analogue revealed to have the quite tight and stable alpha-helical structure using the nuclear magnetic resonance (NMR) analysis. The biological activities of these analogues were examined using a cAMP-generating assay in LLC-PK1 cell lines stably transfected with the wild-type human PTH1 receptor. Only the PTH analogue substituted with methyl moiety without acetylation showed significant cAMP generating action with 15.0 +/- 3.414 of EC50. Then, we used an ovariectomized rat model system to compare the in vivo effects of parathyroid hormone analogue with that of PTH (1-84). Daily subcutaneous administration of the unacetylated Aib1,3PTH (1-14) for 5 weeks in 30 nM/kg subcutaneously with positive control group receiving PTH (1-84) with 8 nM/ kg were performed. However, there was no significant change in spinal or femoral bone mineral density assessed by dual x-ray absorptiometry (DXA) in the Aib1,3PTH (1-14) group where definite increase of these parameters shown in the PTH (1-84) group (p < 0.001). Assessment of bone strength was evaluated with no significant differences among all groups. It was quite disappointing to see the actual discrepancies between the result of significant pharmacokinetic potency and the in vivo clinical effect of the Aib1,3PTH (1-14). However, there are several limitations to mention, such as the short duration of treatment, matter of dosage, and insufficient effect of tight alpha-helical structures with absence of C-terminus. In conclusion, our findings suggest that unacetylated Aib1,3PTH (1-14) did not exhibit any anabolic effects at the bones of ovariectomized rats.
Subject(s)
Rats , Humans , Female , Animals , Transfection , Time Factors , Structure-Activity Relationship , Stress, Mechanical , Spectrometry, X-Ray Emission , Protein Structure, Tertiary , Protein Structure, Secondary , Protein Conformation , Protein Binding , Peptides/chemistry , Parathyroid Hormone/analogs & derivatives , Molecular Sequence Data , Molecular Conformation , Models, Statistical , Models, Molecular , Magnetic Resonance Spectroscopy , LLC-PK1 Cells , Dose-Response Relationship, Drug , Densitometry , Cyclic AMP/metabolism , Cell Line , Bone and Bones/metabolism , Bone Density , Biomechanical Phenomena , Aminoisobutyric Acids/metabolism , Amino Acid Sequence , Alanine/chemistryABSTRACT
The mechanism of protein synthesis is still unknown due to inability to detect the so-called enzyme "peptidyl transferase" even after elucidation of high-resolution crystal structure of ribosome. We have recently shown by model building and semi-empirical energy calculation that the tRNA molecule at P-site of ribosome may act as peptidyl transferase (Das et al. (1999) J. Theor. Biol. 200, 193-205). We proposed that the tetrahedral intermediate formed from nucleophylic attack of CO of P-site amino-acylated tRNA by NH2 of A-site amino-acylated tRNA is converted to a six-member ring intermediate by conformational change. This ring intermediate produces a free tRNA and a tRNA covalently linked to a peptide. However, energy of the six-member ring intermediate was calculated to be quite high. We show here that the energy values of all the reactants, intermediates and products are within the expected range when they are calculated using high level ab initio quantum chemical methods.
Subject(s)
Alanine/chemistry , Binding Sites , Kinetics , Models, Chemical , Peptides/chemistry , Peptidyl Transferases/metabolism , Protein Structure, Tertiary , RNA, Transfer/chemistry , Ribose/chemistry , ThermodynamicsABSTRACT
The results of the structural and conformational studies carried out using 13C CPMAS NMR technique on several glycine and alanine containing peptides in the solid state are reported. The study demonstrates the effects of variations in 13C chemical shifts due to conformation and hydrogen bonding. The possibility of applying this technique to obtain insight into the conformational characteristics of peptides of unknown structures is discussed.