Assuntos
Benzodiazepinas/farmacologia , Caseínas/química , Caseínas/farmacologia , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/farmacologia , Animais , Ansiolíticos/uso terapêutico , Anticonvulsivantes/uso terapêutico , Ansiedade/tratamento farmacológico , Sítios de Ligação , Caseínas/metabolismo , Caseínas/uso terapêutico , Bovinos , Pentilenotetrazol , Fragmentos de Peptídeos/metabolismo , Fragmentos de Peptídeos/uso terapêutico , Ratos , Ratos Wistar , Receptores de GABA-A/metabolismo , Convulsões/induzido quimicamente , Convulsões/tratamento farmacológicoRESUMO
The conformation of the benzodiazepine-like decapeptide, YLGYLEQLLR, corresponding to residues 91-100 of bovine alphaS1-casein, has been examined in SDS micelles using CD, two-dimensional 1H-NMR and restrained molecular-dynamics simulation. Evidence is presented that the decapeptide adopts a rigid structure in water/SDS micellar medium, but not in water or dimethylsulfoxide. The three-dimensional structure, consistent with the proton-proton distances obtained from the quantitative analysis of the two-dimensional NOEs, was generated by restrained energy minimization and molecular-dynamics simulation. In water/SDS micellar medium, YLGYLEQLLR adopts an amphipathic helicoid structure with distinct hydrophobic and hydrophilic faces. The relative disposition of the tyrosine aromatic rings was compared with that of the aromatic rings in the benzodiazepines.
Assuntos
Benzodiazepinas/farmacologia , Caseínas/química , Caseínas/farmacologia , Micelas , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/farmacologia , Conformação Proteica , Animais , Bovinos , Dicroísmo Circular , Dimetil Sulfóxido/farmacologia , Ligação de Hidrogênio , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Fragmentos de Peptídeos/síntese química , Estrutura Secundária de Proteína , Dodecilsulfato de Sódio/farmacologia , Tirosina/química , ÁguaRESUMO
A method for the simultaneous determination of the ratios of the three aromatic amino-acid residues in peptides was set up in acidic conditions. Binary and ternary mixtures of these amino acids were prepared, and first- and second-derivative spectra then calculated from their 0.1 nm resolution spectra between 240 and 320 nm. Certain spectral bands were chosen to differentiate tyrosine from tryptophan on the first-derivative spectra, and phenylalanine from tyrosine and tryptophan on the second-derivative spectra. Variation of the amplitude of the chosen bands was shown to be a linear function of the ratio of the aromatic amino acids in the mixture. This technique was validated with peptides whose sequence was known. The difference between theoretical and experimentally determined ratios was lower than 10%. Since the results are obtained as ratios, neither the concentration nor the nature of the peptide has to be known. The feasibility of application using a photodiode array detector with high resolution in reversed-phase high-performance liquid chromatography is discussed.
Assuntos
Aminoácidos/análise , Peptídeos/química , Sequência de Aminoácidos , Aminoácidos/metabolismo , Animais , Derivados de Benzeno/química , Bovinos , Cromatografia Líquida de Alta Pressão , Dados de Sequência Molecular , Peptídeos/síntese química , Peptídeos/metabolismo , Homologia de Sequência de Aminoácidos , Espectrofotometria Ultravioleta , Triptofano/química , Tirosina/químicaRESUMO
A method for the simultaneous determination of the ratios of three aromatic residues in peptides by derivative UV spectrophotometry on a spectrophotometer with a resolution of 0.1 nm can be used for the RP-HPLC analysis of peptides because of the recent development of high-resolution photodiode-array detectors (1.2 nm). The difference between the theoretical and experimental ratios of aromatic residues of peptides determined in real time is less than 5%. This method could become a powerful tool for the study of peptides and hydrolysates: A variety of possible applications are discussed.
