RESUMO
The chemical nature of the non-tryptophan (non-Trp) fluorescence of porcine and human eye lens proteins was identified by Mass Spectrometry (MS) and Fluorescence Steady-State and Lifetime spectroscopy as post-translational modifications (PTM) of Trp and Arg amino acid residues. Fluorescence intensity profiles measured along the optical axis of human eye lenses with age-related nuclear cataract showed increasing concentration of fluorescent PTM towards the lens centre in accord with the increased optical density in the lens nucleolus. Significant differences between fluorescence lifetimes of "free" Trp derivatives hydroxytryptophan (OH-Trp), N-formylkynurenine (NFK), kynurenine (Kyn), hydroxykynurenine (OH-Kyn) and their residues were observed. Notably, the lifetime constants of these residues in a model peptide were considerably greater than those of their "free" counterparts. Fluorescence of Trp, its derivatives and argpyrimidine (ArgP) can be excited at the red edge of the Trp absorption band which allows normalisation of the emission spectra of these PTMs to the fluorescence intensity of Trp, to determine semi-quantitatively their concentration. We show that the cumulative fraction of OH-Trp, NFK and ArgP emission dominates the total fluorescence spectrum in both emulsified post-surgical human cataract protein samples, as well as in whole lenses and that this correlates strongly with cataract grade and age.
Assuntos
Catarata/diagnóstico , Catarata/genética , Cristalinas/genética , Processamento de Proteína Pós-Traducional/genética , Animais , Catarata/patologia , Cromatografia Líquida de Alta Pressão , Cristalinas/isolamento & purificação , Fluorescência , Humanos , Cristalino/metabolismo , Cristalino/patologia , Espectrometria de Massas , Espectrometria de Fluorescência , Suínos , Triptofano/química , Triptofano/isolamento & purificação , Raios UltravioletaRESUMO
Peptides of varying length (dimers to octamers) were prepared from nucleoside beta-amino acids and conformational studies, based on NOE observations, show that the beta-peptides form an unusual 8-helix.
Assuntos
Aminoácidos/química , Nucleosídeos/química , Peptídeos/química , Espectroscopia de Ressonância Magnética/métodos , Modelos Moleculares , Conformação de Ácido Nucleico , Estrutura Secundária de ProteínaRESUMO
A range of novel N-terminal lipid-functionalized peptide nucleic acid (PNA) monomers have been prepared and their abilities to inhibit HIV-1 reverse transcriptase and integrase have been examined.
Assuntos
Fármacos Anti-HIV/química , Fármacos Anti-HIV/farmacologia , HIV-1/efeitos dos fármacos , Ácidos Nucleicos Peptídicos/química , Ácidos Nucleicos Peptídicos/farmacologia , Fármacos Anti-HIV/síntese química , Desenho de Fármacos , Inibidores de Integrase de HIV/síntese química , Inibidores de Integrase de HIV/química , Inibidores de Integrase de HIV/farmacologia , Transcriptase Reversa do HIV/antagonistas & inibidores , Humanos , Testes de Sensibilidade Microbiana , Ácidos Nucleicos Peptídicos/síntese química , Inibidores da Transcriptase Reversa/síntese química , Inibidores da Transcriptase Reversa/química , Inibidores da Transcriptase Reversa/farmacologiaAssuntos
Acetatos/farmacologia , Farmacorresistência Viral/genética , Guanina/análogos & derivados , Transcriptase Reversa do HIV/antagonistas & inibidores , HIV-1/efeitos dos fármacos , Inibidores da Transcriptase Reversa/farmacologia , Acetatos/química , Guanina/química , Guanina/farmacologia , HIV-1/genética , Cinética , Inibidores da Transcriptase Reversa/químicaRESUMO
8-Benzyloxymethyl-3,4,5-tribenzoyloxy-9-oxa-1-azabicyclo[4.2.1]nonane has been prepared as the single diastereoisomer 8 from an intramolecular 1,3-dipolar cycloaddition involving 2-(benzyloxy)acetaldehyde and omega-unsaturated hydroxylamine 7 derived from methyl alpha-D-glucopyranoside. The analogous 8-methoxycarbonyl 9-oxa-1-azabicyclo[4.2.1]nonane was afforded in a similar manner, from methyl D-galactopyranoside and methyl glyoxylate, as a 3:1 mixture of diastereoisomers 15 and 16. When conducted in achiral ionic liquid 17 this ratio increased to 8:1, and in chiral ionic liquid 18, compound 15 was formed exclusively.
Assuntos
Alcanos/química , Alcanos/síntese química , Óxidos de Nitrogênio/química , Ciclização , Hidroxilação , Estrutura Molecular , EstereoisomerismoRESUMO
A synthetic route to thymine derivatives of (2S,3R)- and (2S,3S)-4-hydroxyvaline has been developed starting from commercially available L-aspartic acid.
Assuntos
Hidroxiprolina/análogos & derivados , Hidroxiprolina/síntese química , Timina/análogos & derivados , Timina/síntese química , Ácido Aspártico , DNA/química , Indicadores e ReagentesRESUMO
All four diastereoisomers of 3-thymine-1-((t)butoxycarbonyl)aminocyclopentane-1-carboxylic acid have been synthesised from (S)-dimethyl malate and thymine monomer 12 has been incorporated into an alpha-cycloPNA oligomer.
Assuntos
Cicloleucina , Ácidos Nucleicos Peptídicos/síntese química , Cicloleucina/química , Indicadores e Reagentes , Estrutura Molecular , Ácidos Nucleicos Peptídicos/química , EstereoisomerismoRESUMO
The initial experiments towards the chemical synthesis of conformationally rigid peptide nucleic acid analogues with azetidine moieties have been described.
Assuntos
Conformação de Ácido Nucleico , Ácidos Nucleicos Peptídicos/química , Ácidos Nucleicos Peptídicos/síntese química , Azetidinas , Conformação ProteicaRESUMO
Steroid sulfatase (STS) is a new target for the endocrine therapy of breast cancer. To ascertain some of the requirements for inhibition of estrone sulfatase activity, a number of novel analogues of estrone 3-O-sulfate possessing sulfate surrogates were synthesized and evaluated as inhibitors of estrone sulfatase (STS) in comparison to a lead inhibitor, estrone-3-O-methylthiophosphonate (E1-3-MTP). Using a selective enzyme digestion, one of the diastereoisomers of this compound, (R(p))-E1-3-MTP, could be prepared and evaluated. From structure-activity studies, we show that chirality at the phosphorus atom, hydrophobicity, basicity, size, and charge all influence the ability of a compound to inhibit estrone sulfatase activity. Of these, hydrophobicity seems to be the most important since simple, active nonsteroidal inhibitors, based on 5,6,7,8-tetrahydronaphth-2-ol (THN), can be prepared, provided that they are lipophilic enough to partition into a nonpolar environment. Also, a negatively charged group is favorable for optimal binding, although it appears that the presence of a potentially cleavable group can compensate for lack of charge in certain cases. A homology model of STS has been constructed from the STS sequence, and molecular docking studies of inhibitors have been performed to broaden the understanding of enzyme/inhibitor interactions. This model clearly shows the positions of the key amino acid residues His136, His290, Lys134, and Lys368 in the putative catalytic region of the formylglycine at position 75, with residues Asp35, Asp36, Asp342, and Gln343 as ligands in the coordination sphere of the magnesium ion. Docking studies using the substrate and estrone-3-sulfate mimics that are active inhibitors indicate they are positioned in the area of proposed catalysis, confirming the predictive power of the model.