A structure-based model for cytochrome P450cam-putidaredoxin interactions

Putidaredoxin (Pdx) is a Fe2S2 ferredoxin which acts as the physiological reductant of cytochrome P-450cam (CYP101). A model for the solution structure of oxidized Pdx has been determined using NMR methods (Pochapsky et al (1994) Biochemistry 33, 6424-6432). 1H-15N correlations and redox-dependent amide exchange rates have also been described (Lyons et al (1996) Protein Sci 5, 627-639). Data obtained from mutagenesis and kinetic measurements concerning the interactions of Pdx and CYP101 are summarized. A model for the structure of the homologous ferredoxin adrenodoxin (Adx) is also described, and data concerning Adx activity are discussed in relation to this structure. The structures of Pdx and CYP101 were used as starting points for molecular modeling and molecular dynamics simulations. Close approach between the metal centers of the two proteins and interaction between aromatic residues on the surfaces of the proteins are premised. The resulting complex exhibits three intermolecular salt bridges, five intermolecular hydrogen bonds and a 12 A distance between the metal centers. The first direct observations of interaction between Pdx and CYP101 (by two-dimensional NMR of 15N-labeled Pdx in solution with CYP101) are described. The results of the NMR experiments indicate that conformational gating of the electron transfer complex between CYP101 and Pdx may be important.     

Aerobically incubated thioglycolate broth disk method for antibiotic susceptibility testing of anaerobes

The anaerobic broth disk (AnBD) method of Wilkins and Thiel and a new modification, designated the thioglycolate broth disk method, were compared with an agar dilution technique. The thioglycolate broth disk method was incubated aerobically (AeTBD) or anaerobically (AnTBD). One hundred anaerobic bacteria representing 15 species were tested with clindamycin, chloramphenicol, erythromycin, penicillin, and tetracycline. Agreement of results by the two methods with minimal inhibitory concentration determinations were: AnBD, 95.2%; AnTBD, 91.5%; AeTBD, 94.5%. With clindamycin, chloramphenicol, and penicillin, the agreement of the AeTBD and agar dilution results was 100%, 100%, and 95%, respectively. Using the AeTBD method, only 1.1% of all tests gave false susceptible readings, whereas 4.4% gave false resistant readings. All susceptibility testing errors occurred with tetracycline, erythromycin, and, to a lesser extent, penicillin. For each method, the changes in designation of bacteria as being susceptible or resistant to an antibiotic between trials primarily involved strains with minimal inhibitory concentrations which were +/- one dilution of the respective breakpoint value. The same situation was true for most bacteria that yielded false resistant readings within each trial. False resistant readings with tetracycline were determined to be unrelated to excess cation content of test media. These results reaffirm the reliability of the AnBD method and indicate that the AeTBD modification is equally reliable. The greater convenience and lower cost of the AeTBD method should make possible more widespread performance of susceptibility testing for anaerobic bacteria in hospital laboratories.     

Analysis of an algorithm that resolves oscillatory data into smoothcomponents

An algorithm for extracting smooth functions from oscillatory data by D.A. Ksienski (1985) was tested for accuracy. It was generally found that the algorithm does not accurately reproduce smooth input functions. Yet, when the smooth functions produced from this algorithm were used for interpolation, satisfactory results were obtained. It is concluded that this algorithm can therefore be utilized for some applications requiring smooth functions     

Attitudes and expectations of 1995 gastroenterology graduates about gastroenterology

OBJECTIVE: To learn more about current attitudes and expectations of recent (June 1995) graduates of gastroenterology fellowship programs, why they chose either a private practice or academic career, and what impact managed care or health care reform had in their decision. METHODS: Between April and June 1995, and 8-page, 35-question survey questionnaire was mailed to graduating fellows and returned for evaluation. RESULTS: Graduates believed managed care had an impact on job availability, but it was not a factor in their job choice. Forty percent of the respondents reported that finding a job was either difficult or very difficult. The majority of respondents (67%) are pursuing a career in private practice. Most private practice physicians (PP) trained in 2-yr programs whereas academic physicians (AC) trained for the most part in 3-yr programs. The principal criteria on which decisions regarding job selection were based were similar between the two groups: co-workers, geographic location, access to patient care, and ability to perform endoscopy. Respondents in PP and AC expected to work 50-70 h/wk, care for patients with similar diseases, and have ample time for family. They would choose GI again as a career and believed that there is a future in GI. Salary expectations varied markedly between the two groups, and AC physicians were more concerned about their future financial needs. Twenty percent of PP physicians and 71% of AC physicians plan to participate in clinical research. CONCLUSIONS: Recent graduates of gastroenterology fellowship programs continue to have high expectations of their future careers. Although some had difficulty finding a job and stated that, although managed care had an impact on the job market, it had not yet become a major factor in their job selection.