Biomedical subjects
Publications and source records attributed to Roberto Cao.
Superoxide dismutase was glycosidated with cyclodextrin-branched carboxymethylcellulose. The modified enzyme contained 1.4 mol polymer per mol protein and retained 87% of the initial activity. The anti-inflammatory activity of superoxide dismutase was 2.2-times increased after conjugation and its plasma half-life time was prolonged from 4.8 min to 7.2 h.
Mannan and carboxymethylcellulose, previously activated by periodate oxidation, were grafted with mono-6-butylenediamino-6-deoxy-beta-cyclodextrin derivatives by reductive alkylation in the presence of sodium borohydride. The formation of supramolecular complexes between these polymers and Naproxen was confirmed by fluorescence spectroscopy. The solubility of the drug was 3.8-4.6 fold increased in the presence of the cyclodextrin-grafted polysaccharides. The in vivo anti-inflammatory property of Naproxen was 1.7 times higher after supramolecular association with beta-cyclodextrin-branched mannan.
Dextran, mannan and carboxymethylcellulose, previously activated by periodate oxidation, were grafted with beta-cyclodextrin moieties by reductive alkylation in the presence of sodium borohydride. These polymers were used as supramolecular carriers for naproxen, improving the "in vivo" anti-inflammatory properties of this drug.
The polysaccharide O-carboxymethyl-poly-beta-cyclodextrin was synthesized (molecular mass 13,000 Da, 40% carboxy groups) and attached to the surface of bovine pancreatic trypsin. The resulting neoglycoenzyme retained high proteolytic and esterolytic activity and contained approx. 1.0 mol of polymer/mol of enzyme. The optimum temperature for trypsin activity was increased by 10 degrees C after this transformation. Thermostability of the polymer-enzyme complex was increased by about 14 degrees C over 10 min incubation. The conjugate was also more resistant to thermal inactivation at different temperatures, ranging from 45 to 60 degrees C, demonstrating the influence of supramolecular and polymer-protein electrostatic interactions on trypsin thermostabilization. Additionally, the conjugate was 36-fold more resistant to the action of the anionic surfactant SDS. This modification also protected the enzyme from autolysis at alkaline pH.
Dopamine can be detected selectively in the presence of ascorbate at a gold electrode modified by a beta-cyclodextrin/thioctic acid mixed monolayer.
Three copper(II) complexes containing beta-cyclodextrin (betaCD) derivatives as ligands [mono-6-methylamino-6-deoxy-betaCD dithiocarbamate (CDTC), mono-6-histamino-6-deoxy-betaCD (CDHM) and mono-6-Nalpha-arginyl-6-deoxy-betaCD (CDARG)] have been studied by electron paramagnetic resonance. The spectra have been recorded at X- and S-bands and different temperatures and simulated to obtain the best set of magnetic parameters. In particular, the 300 K spectra are typical of the slow motion regime, as expected considering the high molecular weight of the ligands. Some structural characteristics of the complexes are proposed on the basis of dynamic and covalency parameters obtained from simulation.
Dextran modified with the mono-6-pentylene-diamino-6-deoxy-beta-cyclodextrin derivative was evaluated as a thermoprotectant additive for trypsin. The optimum temperature for trypsin activity was increased by 7 degrees C in the presence of this polymer. The enzyme thermostability was increased from 48.5 to 64 degrees C over 10 min of incubation, and the activation free energy of thermoinactivation at 50 degrees C was increased by 4.1 kJ/mol in the presence of the additive. Trypsin was 6-fold more resistant to autolytic inactivation at alkaline pH in the presence of the polymer.
This is the first report on the formation of air-stable copper nitrosyl complexes. The interaction of nitric oxide, NO, with Cu(DTC)(2).3H(2)O (DTC: dithiocarbamate) and was studied in aqueous solution at pH 7.4 and 293 K. The stability constants were determined from UV-Vis data, using LETAGROP program. The high values obtained, log beta(1)=9.743(5) and log beta(2)=15.44(2) for Cu(ProDTC)(2)-NO, (ProDTC=L-prolinedithiocarbamate) and log beta(1)=8.723(5) and log beta(2)=11.45(2) for Cu(MorDTC)(2)-NO system, (MorDTC=morpholyldithiocarbamate), indicate the formation of two stable nitrosyl complexes, Cu(DTC)(2)NO and Cu(DTC)(2)(NO)(2). Coordinated NO is neither affected by the presence of air nor when the solution is purged with Ar. Cu(MorDTC)(2)NO.3H(2)O was isolated in the solid state and its nuNO (IR) band at 1682 cm(-1), but affected by temperature variations over 333 K.
Bovine pancreatic trypsin was modified by the mono-6-amino-6-deoxy derivatives of alpha-, beta-, and gamma-cyclodextrin through a transglutaminase-catalyzed reaction. The trypsin-cyclodextrin conjugates, containing about 3 mol of oligosaccharide per mole of protein, were tested for their catalytic and stability properties. The specific esterolytic activity and the kinetics constants of trypsin were significantly improved following the transglutaminase-induced structural modifications. Trypsin-cyclodextrin conjugates were also found markedly (sixfold) more resistant to autolytic degradation at alkaline pH, and their thermal stability profile was improved by about 16 degrees C. Moreover, they were particularly resistant to heat inactivation when treated at different temperatures ranging from 45 degrees C to 70 degrees C for different periods of time.
Streptoverticillum sp. transglutaminase was used as catalyst for the attachment of several beta-cyclodextrin derivatives to the glutamine residues in bovine pancreatic trypsin. The modifying agents used were mono-6-ethylenediamino-6-deoxy-beta-cyclodextrin, mono-6-propylenediamino-6-deoxy-beta-cyclodextrin, mono-6-butylenediamino-6-deoxy-beta-cyclodextrin and mono-6-hexylenediamino-6-deoxy-beta-cyclodextrin. The transformed trypsin preparations contained about 3 mol of oligosaccharides/mol of protein. The specific esterolytic activity of trypsin was increased by about 4-21% after conjugation. The K (m) values for cyclodextrin-trypsin complexes represented about 58-87% of that corresponding to the native enzyme. The optimum temperature for esterolytic activity of trypsin was increased by about 5-10 degrees C after enzymic modification with the cyclodextrin derivatives. The thermostability was increased by 16 degrees C for the modified trypsin. Thermal inactivation at different temperatures ranging from 45 to 60 degrees C was markedly increased for the oligosaccharide-trypsin complexes. This modification also protected the enzyme against autolysis at alkaline pH.
Bovine pancreatic trypsin was chemically modified by a beta-cyclodextrin-carboxymethylcellulose polymer using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide as coupling agent. The conjugate retained 110% and 95% of the initial esterolytic and proteolytic activity, respectively, and contained about 2 mol of polymer per mol of trypsin. The optimum temperature for trypsin was increased to 8 degrees C after conjugation. The thermostability of the enzyme was increased to about 16 degrees C after modification. The conjugate prepared was also more stable against thermal incubation at different temperatures ranging from 45 degrees C to 60 degrees C. In comparison with native trypsin, the polymer-enzyme complex was more resistant to autolytic degradation at pH 9.0, retaining about 65% of the initial activity after 3h incubation. In addition, modification protected trypsin against denaturation in the presence of sodium dodecylsulfate.
Bovine pancreatic alpha -chymotrypsin was chemically modified with two different beta -cyclodextrin derivatives, named mono-6-formyl-beta-cyclodextrin and mono-6-succinyl-6-deoxy-beta-cyclodextrin. The modified enzymes contained approx. 3-5 mol of oligosaccharide/mol of protein, and retained full proteolytic and esterolytic activity. The optimum temperature for alpha -chymotrypsin was increased by 8 degrees C and its thermostability was enhanced by about 4-6 degrees C after modification. The conjugated enzymes were also more resistant to thermal inactivation at temperatures ranging from 45 to 55 degrees C. Additionally, the modified enzymes were 7-fold more stable against incubation at pH 9.0. The possible influence of supramolecular interactions on the thermal stabilization of modified alpha -chymotrypsins was also studied.