Determination of kinetic parameters of penicillin acylases for phenylacetylated compounds is complicated due to the low K(m) values for these substrates, the lack of a spectroscopic signal, and the strong product inhibition by phenylacetic acid. To overcome these difficulties, a spectrophotometric method was developed, with which kinetic parameters could be determined by measuring the effects o...

The antithrombin III (AT III) concentration in plasma was measured in 63 patients on oral anticoagulant treatment (mean age 57.7 years), 26 healthy laboratory controls (mean age 28 years), and 21 patients attending the hypertensive clinic who had never been on oral anticoagulants (mean age 50 years). Three methods were used to measure AT III: a coagulation assay, a chromogenic substrate assay, ...

Enzymatic catalysis of biochemical reactions is essential to all living systems. The "lock and key" and "induced fit" models were early contributions to our understanding of the mechanisms involved in the reaction between an enzyme and its substrate. However, whether a given substrate-induced conformation is rigid or remains flexible has not yet been determined. By measuring the enzyme activity...

AIMS To compare the performance of a new chromogenic medium, Uriselect 4, with cystine lactose electrolyte deficient (CLED) agar and an established chromogenic agar, CPS ID 2 medium, for detection of urinary tract pathogens. METHODS Using a semiquantitative culture method, 777 samples were inoculated on to the three test media in duplicate. All bacterial strains that yielded a potentially sig...

BACKGROUND Selective chromogenic media allowing one-step meticillin-resistant Staphylococcus aureus (MRSA) isolation and identification are widely used. However, the changing epidemiology of MRSA means that the suitability of these chromogenic media requires investigation. AIM To evaluate the following chromogenic media - Colorex MRSA, MRSA Select II, ChromID MRSA, and MRSA Brilliance 2 - for...