[en] We introduce a simple theoretical approach for an equilibrium study of proteins with known native-state structures. We test our approach with results on well-studied globular proteins, chymotrypsin inhibitor (2ci2), barnase, and the alpha spectrin SH3 domain, and present evidence for a hierarchical onset of order on lowering the temperature with significant organization at the local level even at high temperatures. A further application to the folding process of HIV-1 protease shows that the model can be reliably used to identify key folding sites that are responsible for the development of drug resistance

[en] Trypsin and chymotrypsin inhibitor activities of safflower oilcake were studied before and after irradiation. The various doses to which samples were exposed ranged from 7 Gy to 10 kGy. The trypsin inhibitor is inactivated at 42 Gy, whereas the chymotrypsin inhibitor remains active, even at the much higher dose of 10 kGy. Thein vitro digestibility values also showed a significant improvement after irradiation. Exposure to a low dose of 42 Gy is sufficient to improve the nutritional value of the oilcake

No abstract available

[en] Full text: α-Trypsin is a serine-protease with a polypeptide chain of 223 amino acid residues and six disulfide bridges. It is a globular protein with predominance of antiparallel β-sheet secondary structure and it has two domains with similar structures. In the present work, a stability study of α-trypsin in the acid pH range was performed and physical-chemical denaturation parameters were measured by using differential scanning calorimetry (DSC). The α-trypsin has a shelf-life (t_95%) of about ten months at pH 3.0 and 4 deg C and its hydrolysis into the Ψ-trypsin isoform is negligible during six months as monitored by mass spectrometry (Micromass Q-ToF). The observed ΔH_cal/ΔH_vH ratio is close to unity for α-trypsin denaturation, which suggests the occurrence of a two-state transition, devoid of molten-globule intermediates. At pH 3.0, α-trypsin unfolded with T_m 325.9 K and ΔH= 99.10 kcal mol^-1, and the change in heat capacity between the native and unfolded forms of the protein was estimated to be 1.96 ± 0.18 kcal mol^-1 K^-1. The stability of α-trypsin calculated at 298 K and at pH 3.0 was ΔG_U = 6.10 kcal mol^-1. These values are in the range expected for a small globular protein. These results show that the thermodynamic parameters for unfolding of β-trypsin do not change substantially after its conversion to α-trypsin

[en] The effects of heat treatment and enzymic digestion on the antigenic reactivity of ovomucoid were studied. This reactivity was mainly examined by a solid phase competitive radioimmunoassay. The trypsin inhibitory activity was also measured to elucidate its relationship to the antigenic reactivity. The antigenic reactivity and trypsin inhibitory activity diminished in parallel with increase of heating time. However, enzymic digestion caused a more rapid decrease in antigenic reactivity than in trypsin inhibitory activity. From these results, it is suggested that the structure of the antigenic determinants is destroyed in a similar manner to that of the trypsin inhibitory active site when ovomucoid is heated, while the former structure is destroyed more easily than the latter by enzymic digestion

No abstract available

No abstract available

[en] The association of porcine trypsin with soybean trypsin inhibitor (Kunitz) resulted in characteristic changes in absorption spectrum, indicating an alteration of the micro environments of the enzyme chromophores as a consequence of the interaction. The rates of formation of the stable trypsin - inhibitor complexes from porcine - alpha - trypsin and soybean trypsin inhibitor and from porcine - beta - trypsin and either intact or modified soybean trypsin inhibitor were measured by mixing the equimolar concentration of the reactants in a Stopped - Flow apparatus at pH (4.5 to 10.0). The reaction of trypsin with soybean trypsin inhibitor was of first order with respect to the concentration of the reactants used. The rates of dissociation of the stable complexes, alpha - trypsin - soybean trypsin inhibitor, beta -trypsin - soybean trypsin inhibitor and beta -trypsin modified soybean trypsin inhibitor were also measured at pH (1.92 to 3.58). The values of first order rate constant, k/sub D/ obtained for the dissociation of all the three complexes were identical with one another. The kinetics results obtained for the porcine trypsin were compared with those of bovine trypsin system and it was suggested that the reaction mechanisms in both these systems were identical. (author)

[en] Several clinically important proteins and enzymes (bovine serum albumine, glucose oxidase, streptokinase, chymotrypsine and dispase) have been immobilized to fine magnetic particles by means of 1-[3-(dimethylamino) propyl]-3-ethylcarbodiimide hydrochloride (CDI) as a coupling agent. The coupling reactions of these substances were carried out under different sets of conditions (change the pH of the reaction mixture in areas from 4.5 to 6.5 and proportion of magnetic particles to proteins and CDI) to determine the optimum conditions of the immobilization. The usefulness of the presented method is discussed for biomedical and biotechnological applications

[en] The enzymatic activity of a protease was electrically detected using nanopore recordings. A peptide substrate was tethered to microscale beads, and cleavage by the enzyme trypsin released a soluble fragment that was electrophoretically driven through the α-hemolysin protein pore, leading to detectable blockades in the ionic current. Owing to its simplicity, this approach to sense enzymatic activity may be applied to other proteases.