First synthesis of a fully active spin-labeled peptide hormone.

For the first time in the electron spin resonance (ESR) and peptide synthesis fields, a fully active spin-labeled peptide hormone was reported. The ESR spectra of this alpha-melanocyte stimulating hormone (alpha-MSH) analogue (acetyl-Toac0-alpha-MSH) where Toac is the paramagnetic amino acid probe 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid, suggested a pH-independent conformation and a more restricted movement comparatively to the free Toac. Owing to its equivalent biological potency in a skin pigmentation assay as compared to the native alpha-MSH and its unique characteristic (paramagnetic, naturally fluorescent and fully active), this analogue is of great potential for investigation of relevant physiological roles reported for alpha-MSH.

Comparative EPR and fluorescence conformational studies of fully active spin-labeled melanotropic peptides.

Similar to melanocyte stimulating hormone (alpha-MSH), its potent and long-acting analogue, [Nle(4), D-Phe(7)]alpha-MSH, when labeled with the paramagnetic amino acid probe 2,2,6,6-tetramethylpiperidine-N-oxyl-4-amino-4-carboxylic acid (Toac), maintains its full biological potency, thus validating any comparative structural investigations between the two labeled peptides. Correlation times, calculated from the electron paramagnetic resonance signal of Toac bound to the peptides, and Toac-Trp distances, estimated from the Toac fluorescence quenching of the Trp residue present in the peptides, indicate a more rigid and folded structure for the potent analogue as compared to the hormone, in aqueous medium.

Bloqueio do plexo braquial em jumento - relato de caso / Brachial plexus block in donkey - case report

A anestesia locorregional reduz o requerimento de agentes inalatórios e diminui as respostas autonômicas a estímulos cirúrgicos nocivos. Objetiva-se descrever um bloqueio anestésico do plexo braquial guiado por neuroestimulador em jumento, submetido à amputação do membro anterior direito. Foi realizada medicação pré-anestésica com detomidina 0,01mg.kg-1, indução com diazepam 0,05mg.kg-1 e cetamina 2mg.kg-1, todos pela via intravenosa (IV), e a manutenção da anestesia com isoflurano. O plexo braquial foi bloqueado por acesso subescapular, sendo usado neuroestimulador. Utilizou-se 1mg.kg-1 de bupivacaína 0,5% sem vasoconstritor, associada a 1mg.kg-1 de lidocaína 2% sem vasoconstrictor. Os valores de FC e ƒ durante o procedimento cirúrgico variaram de 62 a 78bpm e de 24 a 32rpm, respectivamente. Foram coletadas quatro amostras de sangue para dosagem de cortisol. Este, antes da aplicação da medicação pré-anestésica, foi de 6,4µg/dL e, 30 minutos após a MPA, foi de 2,8µg/dL. A recuperação anestésica foi rápida e sem complicações. O bloqueio do plexo braquial guiado por neuroestimulador mostrou-se eficaz em jumentos, fornecendo analgesia e anestesia satisfatória.(AU)

Locoregional anesthesia reduces the requirement for inhaled agents and reduces the autonomic responses to noxious surgical stimuli. The aim of this study was to describe an anesthetic block of the brachial plexus guided by a neurostimulator in a donkey submitted to right limb amputation. Preanesthetic medication was performed with detomidine 0.01mg.kg-1 induction with diazepam 0.05mg.kg-1 and ketamine 2mg.kg-1 all intravenously, and maintenance of anesthesia with isoflurane. The brachial plexus was blocked by subscapular access, using a neurostimulator. For this purpose, 1mg.kg -1 of bupivacaine 0.5%, without vasoconstrictor, and 1mg.kg- 1 of lidocaine 2%, without vasoconstrictor were used. The values of HR and ƒ during the surgical procedure ranged from 62 to 78bpm, and 24 to 32bpm, respectively. Four blood samples were collected for cortisol dosing. This, prior to the application of the pre-anesthetic medication was 6.4µg/dL and 30 minutes was 2.8µg/dL. Anesthesia recovery was rapid and uncomplicated. Neurostimulator-guided brachial plexus blockade proved to be effective in donkeys, providing satisfactory analgesia and anesthesia.(AU)

Bloqueio do plexo braquial em jumento - relato de caso / Brachial plexus block in donkey - case report

A anestesia locorregional reduz o requerimento de agentes inalatórios e diminui as respostas autonômicas a estímulos cirúrgicos nocivos. Objetiva-se descrever um bloqueio anestésico do plexo braquial guiado por neuroestimulador em jumento, submetido à amputação do membro anterior direito. Foi realizada medicação pré-anestésica com detomidina 0,01mg.kg-1, indução com diazepam 0,05mg.kg-1 e cetamina 2mg.kg-1, todos pela via intravenosa (IV), e a manutenção da anestesia com isoflurano. O plexo braquial foi bloqueado por acesso subescapular, sendo usado neuroestimulador. Utilizou-se 1mg.kg-1 de bupivacaína 0,5% sem vasoconstritor, associada a 1mg.kg-1 de lidocaína 2% sem vasoconstrictor. Os valores de FC e ƒ durante o procedimento cirúrgico variaram de 62 a 78bpm e de 24 a 32rpm, respectivamente. Foram coletadas quatro amostras de sangue para dosagem de cortisol. Este, antes da aplicação da medicação pré-anestésica, foi de 6,4µg/dL e, 30 minutos após a MPA, foi de 2,8µg/dL. A recuperação anestésica foi rápida e sem complicações. O bloqueio do plexo braquial guiado por neuroestimulador mostrou-se eficaz em jumentos, fornecendo analgesia e anestesia satisfatória.(AU)

Locoregional anesthesia reduces the requirement for inhaled agents and reduces the autonomic responses to noxious surgical stimuli. The aim of this study was to describe an anesthetic block of the brachial plexus guided by a neurostimulator in a donkey submitted to right limb amputation. Preanesthetic medication was performed with detomidine 0.01mg.kg-1 induction with diazepam 0.05mg.kg-1 and ketamine 2mg.kg-1 all intravenously, and maintenance of anesthesia with isoflurane. The brachial plexus was blocked by subscapular access, using a neurostimulator. For this purpose, 1mg.kg -1 of bupivacaine 0.5%, without vasoconstrictor, and 1mg.kg- 1 of lidocaine 2%, without vasoconstrictor were used. The values of HR and ƒ during the surgical procedure ranged from 62 to 78bpm, and 24 to 32bpm, respectively. Four blood samples were collected for cortisol dosing. This, prior to the application of the pre-anesthetic medication was 6.4µg/dL and 30 minutes was 2.8µg/dL. Anesthesia recovery was rapid and uncomplicated. Neurostimulator-guided brachial plexus blockade proved to be effective in donkeys, providing satisfactory analgesia and anesthesia.(AU)

Fmoc-POAC: [(9-fluorenylmethyloxycarbonyl)-2,2,5,5-tetramethylpyrrolidine-N-oxyl-3-amino-4-carboxylic acid]: a novel protected spin labeled beta-amino acid for peptide and protein chemistry.

The stable free radical 2,2,6,6-tetramethylpiperidine-N-oxyl-4-amino-4-carboxylic acid (TOAC) is the only spin labeled amino acid that has been used to date to successfully label peptide sequences for structural studies. However, severe difficulty in coupling the subsequent amino acid has been the most serious shortcoming of this paramagnetic marker. This problem stems from the low nucleophilicity of TOAC's amine group towards the acylation reaction during peptide chain elongation. The present report introduces the alternative beta-amino acid 2,2,5,5-tetramethylpyrrolidine-N-oxyl-3-amino-4-carboxylic acid (POAC), potentially useful in peptide and protein chemistry. Investigations aimed at addressing the stereochemistry of this cyclic molecule through X-ray diffraction measurements of crystalline and bulk samples revealed that it consists only of the trans conformer. The 9-fluorenylmethyloxycarbonyl group (Fmoc) was chosen for temporary protection of the POAC amine function, allowing insertion of the probe at any position in a peptide sequence. The vasoactive octapeptide angiotensin II (All, DRVYIHPF) was synthesized by replacing Pro7 with POAC. The reaction of Fmoc-POAC with the peptidyl-resin occurred smoothly, and the coupling of the subsequent amino acid showed a much faster reaction when compared with TOAC. POAC7-AII was obtained in good yield, demonstrating that, in addition to TOAC, POAC is a convenient amino acid for the synthesis of spin labeled peptide analogues. The present findings open the possibility of a wide range of chemical and biological applications for this novel beta-amino acid derivative, including structural investigations involving its differentiated bend-inducing characteristics.