ABSTRACT
Objective: To investigate the interaction between ciprofloxacin (CIP) and ferric-ion binding protein (FBP) from pathogenic bacteria, so as to determine whether FBP is the target of CIP. Methods: Reactions between ciprofloxacin and FBP from N. gonorrhoeae, which was expressed in E. coli, were monitored by UV-visible and NMR spectroscopy. Results: Fe3+ was removed from holo-FBP by CIP in 10 mmol/L Tris-Cl buffer, pH 7.40, at 298 K, and half of the loaded Fe3+ was taken off when 50 molar equivalence of CIP was present. Conclusion: CIP can remove Fe3+ from holo-FBP, indicating that CIP can interfere with the Fe3+ capture of the bacteria and influence the growth and virulence of the bacteria.
ABSTRACT
Objective: To determine the rate constants for the cleavage of pyrophosphate to phosphate by human serum apo-transferrin.Methods: The cleavage was followed by31P NMR spectroscopy.The data for concentration changes of pyrophosphate (as determined from its NMR peak intensity) with time,in the absence and the presence of MgCl2,at different pH values,were fitted to give second order rate constants.Results: The rate constants at 312 K were 8.83×10-4 L·mmol-1·h-1 at pH 6.85,9.59×10-4 L·mmol-1·h-1 at pH 7.4,and 1.38×10-3 L·mmol-1·h-1 at pH 8.15,for reactions of apo-transferrin (0.5-1.0 mmol/L) with 5 molar equivalence of pyrophosphate.The rate constant increased to 1.21×10-3 L·mmol-1·h-1 at pH 7.4,312 K when 2 mmol/L MgCl2 was added.Conclusion: The cleavage of pyrophosphate to phosphate by human serum apo-transferrin is very slow and follows the second-order kinetics.Mg2+ can slightly enhance the rate of the cleavage.
ABSTRACT
Objective: To determine the rate constants for the cleavage of pyrophosphate to phosphate by human serum apo-transferrin.Methods: The cleavage was followed by31P NMR spectroscopy.The data for concentration changes of pyrophosphate (as determined from its NMR peak intensity) with time,in the absence and the presence of MgCl2,at different pH values,were fitted to give second order rate constants.Results: The rate constants at 312 K were 8.83×10-4 L·mmol-1·h-1 at pH 6.85,9.59×10-4 L·mmol-1·h-1 at pH 7.4,and 1.38×10-3 L·mmol-1·h-1 at pH 8.15,for reactions of apo-transferrin (0.5-1.0 mmol/L) with 5 molar equivalence of pyrophosphate.The rate constant increased to 1.21×10-3 L·mmol-1·h-1 at pH 7.4,312 K when 2 mmol/L MgCl2 was added.Conclusion: The cleavage of pyrophosphate to phosphate by human serum apo-transferrin is very slow and follows the second-order kinetics.Mg2+ can slightly enhance the rate of the cleavage.