Biomedical subjects

M T Miranda

Publications and source records attributed to M T Miranda.

9 recordsLinked to original sources

PubMed1991

Thermolysin as a catalyst in enzymatic synthesis of asparagine-containing peptides II.

Thermolysin was used as a catalyst to obtain the following protected di- and tripeptide esters: Z-Asn-Leu-OEt, Z-Asn-Phe-OEt, Moz-Asn-Leu-Gly-OEt, Boc-Asn-Leu-Gly-OEt, Z-Asn-Leu-Gly-OEt, Moz-Asn-Leu-Gly-OBzl, Moz-Asn-Leu-Gly-OtBu, Moz-Gln-Leu-Gly-OEt, Moz-Asn-Ile-Gly-OEt, and Moz-Asn-Leu-Ala-OEt. These compounds were obtained in pure form and the yields exceeded 50%, except for Moz-Asn-Leu-Gly-OtBu and Boc-Asn-Leu-Gly-OEt. H-Cys(Bzl)-OtBu and H-Cys(Bzl)-Pro-Leu-Gly-NH2 were both inadequate as amino components for obtaining Moz-Asn-Cys(Bzl)-OtBu, Z-Asn-Cys(Bzl)-OtBu and Moz-Asn-Cys(Bzl)-Pro-Leu-Gly-NH2 in the thermolysin-catalyzed reactions. In the attempted synthesis of the protected pentapeptide amide, this protease cleaved the Pro-Leu bond of the amino component H-Cys(Bzl)-Pro-Leu-Gly-NH2 and catalyzed the coupling between the resulting dipeptide amide and Moz-Asn-OH, thus yielding Moz-Asn-Leu-Gly-NH2 as the main product.

Amino Acid Sequence↗

PubMed1991

Transesterification of Moz-Asn-Leu-Gly-OEt in methanol. Confirmation of Ca2+ mediated catalysis.

During the recrystallization of the crude protected tripeptide ester Moz-Asn-Leu-Gly-OEt (obtained by an enzymatic coupling reaction) in methanol/water, the transesterification of this compound to methyl ester was observed. The involvement of Ca2+ in this process was indicated by the results obtained in the following experiments: 1) incubation of crude Moz-Asn-Leu-Gly-OEt in methanol solutions of o-phenanthroline and EDTA; 2) recrystallization of the crude Moz-Asn-Leu-Gly-OEt in ethanol/water followed by incubation in methanol; 3) determination of the Ca2+ content of the crude Moz-Asn-Leu-Gly-OEt. After recrystallization Moz-Asn-Leu-Gly-OEt lost the ability to be transesterified in methanol. However, in the presence of crude Moz-Asn-Leu-Gly-OEt, or calcium acetate, or a mixture of calcium chloride/sodium acetate, the compound was transesterified, suggesting that the transesterification of crude and recrystallized compounds occurs through different mechanisms. On the basis of these results, and of the conformational data obtained for these peptides by 1H-NMR, we suggest models for the transesterification reactions.

Amino Acid Sequence↗

PubMed1991

Transesterification of peptide esters and peptidyl resins in methanol-containing calcium acetate.

The following crude peptide derivatives obtained by thermolysin catalysis in the presence of calcium acetate, were dissolved in methanol and in methanol-containing calcium acetate to determine the possible occurrence of transesterification: Z-Asn-Leu-Gly-OEt, Boc-Asn-Leu-Gly-OEt, Moz-Asn-Leu-Gly-OBzl, Moz-Asn-Leu-Gly-OtBu, Moz-Gln-Leu-Gly-OEt, Moz-Asn-Ile-Gly-OEt, and Moz-Asn-Leu-Ala-OEt. Only Z-Asn-Leu-Gly-OEt and Moz-Gln-Leu-Gly-OEt were transesterified in methanol, indicating the existence of a peptide derivative-Ca2+ catalytic complex that may favor the reaction. In the presence of calcium acetate, all protected peptide esters except the t-butyl esters were transesterified. The transesterification of several other di- and tripeptide derivatives of different structures in methanol-containing calcium acetate was detected by HPLC and confirmed by the isolation and characterization of some of the protected peptide methyl esters obtained. Boc-Leu-Gly- and Moz-Asn-Leu-Gly-Merrifield resin were also transesterified in these solutions.

Acetates↗

PubMed1988

Thermolysin and alpha-chymotrypsin mediated synthesis of tripeptides containing proline.

The tripeptides Z-Pro-Leu-Gly-OEt, Z-Pro-Leu-Gly-NH2 and Z-Pro-Leu-Gly-OBzl were synthesized by thermolysin and alpha-chymotrypsin catalysis. The optimum conditions for the couplings between Z-Pro-OH and H-Leu-OEt or H-Leu-Gly-OEt catalysed by thermolysin were determined by a systematic study involving analysis of pH effect, ammonium sulfate concentration, reaction time, enzyme concentration, and relative proportion of the carboxyl and amine components. The best yield obtained for Z-Pro-Leu-OEt was 77% and for Z-Pro-Leu-Gly-OEt, 100%. Z-Pro-Leu-OEt was coupled to H-Gly-OEt, H-Gly-NH2 and H-Gly-OBzl. The best conditions to obtain Z-Pro-Leu-Gly-OEt and Z-Pro-Leu-Gly-NH2 were determined by the study of some factors that affect the reaction yield, such as organic solvent presence, substrate ratio and aqueous and organic solvent ratio. The yield obtained under optimum synthesis conditions was 55% for Z-Pro-Leu-Gly-OEt and 61% for Z-Pro-Leu-Gly-NH2. Z-Pro-Leu-Gly-OBzl was synthesized with 42% yield.

Chymotrypsin↗

PubMed1988

Production of monoclonal antibodies to Sp2/O-Ag 14 myeloma cells.

The hybridoma technology developed by Kohler and Milstein allows the obtention of antibodies of a single specificity (i.e. monoclonal antibodies). This methodology was first introduced in the Immunology Laboratory of the Department of Microbiology at the Medical Sciences Campus (MSC), University of Puerto Rico (UPR) in 1986. The production of monoclonal antibodies to Sp2/O-Ag 14 reported herein describes the procedure used and is of importance because it constitutes the first work on monoclonal antibodies performed at our institution and in Puerto Rico.

Animals↗

PubMed1984

The influence of plasma renin substrate on the relationship between plasma renin activity and plasma renin concentration. An experimental study in hyper- and hypothyroid rats.

The effects of endogenous Plasma Renin Substrate (PRS) on the relationship between Plasma Renin Activity (PRA) and the Plasma Renin Concentration (PRC) have been studied in hyperthyroid rats, by I-triiodothyronine (T3) administration and in hypothyroid rats, by propylthiouracil (PTU) treatment, to clarify if PRA changes are an adequate index for evaluating the renin-angiotensin changes during the alterations in the thyroid function. Although in experimental situations studied the induced variation on PRC explains a 62 per cent of the changes in PRA, finding a good lineal correlation between both parameters (r = 0.79, P less than 0.001). Not only does PRS play an important role on the kinetic of the enzymatic reaction but also explains jointly with PRC up to a 85 per cent of PRA alterations. PRS changes become more important during thyrotoxicosis where they limit in a higher degree the velocity of reaction due to inverse relationship between PRC and PRS (r = 0.74, P less than 0.001).

Angiotensinogen↗

PubMedDate not supplied

Influence of thyroid hormone deficiency in DNA contents in different areas of adult rat brain.

We have studied DNA concentrations in various regions of the adult rat brain in prolonged hypothyroidism of different origin. In both normal and hypothyroid rats hypophysis, cerebellum and hypothalamus contained the highest concentrations of DNA. Hypothyroidism produced a slight decrease in DNA content but this effect varied according to the different regions. These variations were due to changes in their maturation period, a critical and specific target for thyroid hormone action after birth.

Animals↗

PubMedDate not supplied

[Combined use of rose Bengal and indirect immunofluorescence in the diagnosis of brucellosis].

In the present prospective study we have evaluated the sensitivity, specificity and predictive value of the Bengal rose and indirect immunofluorescence (IIF) in 122 patients with a bacteriological diagnosis of brucellosis. The sensitivity of the Bengal rose was 95.79% and its specificity 98.43%. IIF had a sensitivity of 68.80% and a specificity of 100% when the polyvalent anti-IgS conjugate was used. The combined parallel use of Bengal rose and IIF-IgS resulted in a sensitivity of 89.17% and a specificity of 100%. There was a good correlation between Bengal rose and serum agglutination test (r = 0.72); on the contrary, there were not good correlations between the fluorescent conjugates and Bengal rose, agglutination and Coombs test. In conclusion, the combined use of Bengal rose as a screening test and IIF as a confirmation study is a good diagnostic strategy for human brucellosis.

Agglutination Tests↗

PubMedDate not supplied

[Shock].

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Nursing↗