Characterization of the ultraviolet absorption spectra of p-substituted derivatives of benzamidine

Electronic effects in the interaction of para-substituted benzamidines with trypsin: the involvement of the .pi.-electronic density at the central atom of the substituent in binding

“…The spectral properties of the probe have previously been studied. 26 The binding of benzamidine to trypsin causes a change in the inhibitor spectral properties which can be detected by difference spectroscopy, as shown in Figure 1.…”

“…The spectra were taken at 25.0 °C. The values of the bathochromic shifts were taken from the work of Rogana, et al 26 The parameters are: r = 0.6974, slope = 0.9654 ± 0.3506; intercept = -3.6318. The same plot also shows the corresponding changes in the standard free energy of dissociation at 15 °C.…”

“…The pKa values for the amidines were obtained by spectrophotometric titration in the ultraviolet, as will be described in the work of Rogana, Leite, Mares-Guia, and Nelson. 29 The calculation of the pAa and the statistical analysis of the data were carried out with the help of a computer program called linea.30 The binding of benzamidine to trypsin was also measured by titration using difference spectroscopy in the region of ultraviolet, with the Perkin-Elmer Model 450 instrument, using the technique described by East and Trowbridge.33 The sample cell contained enzyme and benzamidine in one compartment and Tris buffer in the other. The reference cell contained benzamidine in one compartment and trypsin in the other.…”

Synthesis and mesomorphic properties of some disubstituted unsymmetrical phenyl-1,2,4,5-tetrazines

“…The reaction mixture was placed under N2, allowed to warm to room temperature and after 64 h diluted with abs EtOH (50ml). This solution and a solution of 4-bromobenzamidine hydrochloride [27] (3.3 g, 14 mmol) were added dropwise and simultaneously within 15min to a stirred solution of hydrazine hydrate (9.9g, 309mmol) in abs EtOH (30ml) at 0°C. The ice bath was removed and the reaction mixture stirred 3 h at room temperature.…”

The Binding Mechanism of a Peptidic Cyclic Serine Protease Inhibitor

“…Their concentrations were determined, using extinction coefficients for the peptides calculated with Protparam § and an experimentally determined extinction coefficient of 1.529 × 10 4 M − 1 cm − 1 at 292 nm for p-aminobenzamidine. 29 In all cases, experiments were designed to provide a fully saturated titration profile with enough signal and curvature to allow precise determination of thermodynamic parameters. The concentration of uPA used in the ∼1.4 -ml sample cell was 5-15 μM, depending on the affinity of the ligand.…”