RESUMEN
Herein, we report an efficient route for the asymmetric synthesis of ß(2)-aminoxy acids as well as experimental and theoretical studies of conformations of peptides composed of ß(2)-aminoxy acids. The nine-membered-ring intramolecular hydrogen bonds, namely, ß N-O turns, are generated between adjacent residues in those peptides, in accordance with our computational results. The presence of two consecutive homochiral ß N-O turns leads to the formation of ß N-O helical structures in solution, although both helical (composed of two ß N-O turns of the same handedness) and reverse-turn (composed of two ß N-O turns with opposite handedness) structures are of similar stability, as suggested by theoretical studies. Nevertheless, two slightly different conformations, with the same handedness, of ß(2)-aminoxy monomers have been observed in the solid state and in solution according to our X-ray and 2D NOESY studies.
Asunto(s)
Péptidos/síntesis química , Enlace de Hidrógeno , Modelos Teóricos , Nitrógeno/química , Oxígeno/química , Péptidos/química , Estructura Secundaria de ProteínaRESUMEN
Disulfide-bond formation between the side chains of cysteine-cysteine pairs is often critical to the folding behavior, stability, and functionality of proteins. In this paper, we report that sulfur atoms can be introduced into the amide groups of aminoxy peptides to form a novel type of disulfide bridge, which creates a connecting loop in the peptide backbone.
Asunto(s)
Aminas/química , Disulfuros/química , Óxidos/química , Péptidos/química , Espectroscopía de Resonancia Magnética , Modelos Moleculares , Estructura Molecular , Péptidos/síntesis química , Espectrofotometría , Compuestos de Sulfhidrilo/químicaRESUMEN
OBJECTIVE: To investigate the features of BP, HR, cerebral blood flow (CBF) and heart rate variation (HRV) during sequential head-up tilt table test (HUT) and provide information for methodology of testing tendency to syncope in pilots. METHOD: Sixteen healthy male were exposed to HUT +45 degrees 20 min, +60 degrees 20 min, and +75 degrees 20 min respectively with 5 min rests in between. CBFV, HR, HRV, BP were measured with transcranial doppler image (TCI), 12-Lead in phase ECG. RESULT: 1) As the tilt angle became larger, HR and DBP increased gradually (P<0.05), with SBP, PP and CBF Velocity (Vs,Vm,Vd) descended. There were significant differences among the various conditions. CV became smaller before +75 degrees, and then it began to increase. 2) Correlation between physiological indices and techno-indices were analyzed. At the point of 1 min, tilt angle was significantly positively correlated with SBP, DBP, MAP, Vd, and sdRR (P<0.01); At the point of 20 min, tilt angle was significantly positively correlated with HR and sdRR (P<0.01), but negatively correlated with SBP, PP, Vs and mRR (P<0.01), time of exposure was positively correlated with HP (P< 0.01), but negatively correlated with Vm, Vd, and mRR (P<0.01). 3) Correlation among physiological indices were also analyzed. HR were negatively correlated with SBP, Vs, Vm and Vd (P<0.01), SBP were significantly positively correlated with Vd, and mRR (P<0.01). Vs, Vm, Vd were significantly positively correlated with mRR and sdRR (P< 0.01). CONCLUSION: By investigating HR, BP, HRV and CBFV during of different angles, some advises for evaluating the tendency to syncope in pilots were put forward.