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C Woodward

Publications and source records attributed to C Woodward.

At least 91 records · Page 5Linked to original sources
PubMed1987

Hydrogen exchange kinetics of bovine pancreatic trypsin inhibitor beta-sheet protons in trypsin-bovine pancreatic trypsin inhibitor, trypsinogen-bovine pancreatic trypsin inhibitor, and trypsinogen-isoleucylvaline-bovine pancreatic trypsin inhibitor.

Hydrogen exchange rates of six beta-sheet peptide amide protons in bovine pancreatic trypsin inhibitor (BPTI) have been measured in free BPTI and in the complexes trypsinogen-BPTI, trypsinogen-Ile-Val-BPTI, bovine trypsin-BPTI, and porcine trypsin-BPTI. Exchange rates in the complexes are slower for Ile-18, Arg-20, Gln-31, Phe-33, Tyr-35, and Phe-45 NH, but the magnitude of the effect is highly variable. The ratio of the exchange rate constant in free BPTI to the exchange rate constant in the complex, k/kcpIx, ranges from 3 to much greater than 10(3). Gln-31, Phe-45, and Phe-33 NH exchange rate constants are the same in each of the complexes. For Ile-18 and Tyr-35, k/kcpIx is much greater than 10(3) for the trypsin complexes but is in the range 14-43 for the trypsinogen complexes. Only the Arg-20 NH exchange rate shows significant differences between trypsinogen-BPTI and trypsinogen-Ile-Val-BPTI and between porcine and bovine trypsin-BPTI.

Animals↗
PubMed1987

Assignment of asparagine-44 side-chain primary amide 1H NMR resonances and the peptide amide N1H resonance of glycine-37 in basic pancreatic trypsin inhibitor.

New assignments of three previously undetected amide proton NMR resonance lines in bovine pancreatic trypsin inhibitor are reported. These are the peptide amide proton of Gly-37 and the primary amide protons of Asn-44. Specific assignments of Asn-44 and Asn-43 HE and HZ resonances are also reported. The Gly-37 NH and Asn-44 HZ resonances are shifted upfield to 4.3 and 3.4 ppm, respectively, by the ring current of the Tyr-35 aromatic group, while Asn-44 HE resonates at 7.8 ppm. The abnormal chemical shifts of Asn-44 HZ and Gly-37 NH indicate that both NH's interact with the pi-electron cloud of the Tyr-35 ring. This is consistent with their location in the crystal structure. The resonances are resolved by differential labeling techniques and are studied by combined use of NOE and exchange difference spectroscopy.

Amides↗
PubMed1987

Hydrogen exchange kinetics of surface peptide amides in bovine pancreatic trypsin inhibitor.

The acid and base catalytic rate constants, kH, obs and kOH, obs and the pH at the minimum rate, pHmin, of 25 rapidly exchanging protons in bovine pancreatic trypsin inhibitor have been determined. Here we report the labeling procedure giving 1H nuclear magnetic resonance spectral resolution of seven additional rapidly exchanging NH protons and the pH dependence of their chemical shifts. Values of kH,obs kOH,obs and pHmin are given for Ala16, Gly28 and Arg53 NH groups, the only backbone amide protons with static accessibility of more than zero in the crystal structure not previously reports, and for Gly56 NH, buried at the C terminus of an alpha-helix. All four protons reported here have pH min greater than or equal to 3. Conclusions of the previous study predict that peptide protons with pHmin higher than those of model compounds have greater static accessibility of the peptide O than of the peptide N atom. The locations in the crystal structure of the four NH groups whose exchange rates are reported here are in qualitative agreement with these predictions. The ionic strength dependence of Ala16 at pH 5.5 shows a sharp increase in the exchange rate with decreasing salt concentration, as expected for base-catalyzed exchange in a positive electrostatic field.

Amides↗
PubMed1985

Hydrogen kinetics of peptide amide protons at the bovine pancreatic trypsin inhibitor protein-solvent interface.

Hydrogen exchange rate constants of the 25 most rapidly exchanging peptide amide protons in bovine pancreatic trypsin inhibitor have been determined over a range of pH that spans pH min, the pH of minimum rate. Most of these are on the protein surface, exposed to solvent and not hydrogen bonded in the crystal structure. Contrary to commonly held assumptions, the exchange kinetics of surface NH groups are not equivalent to the kinetics of NH groups in peptides in the extended configuration. All surface NH groups exchange more slowly than NH groups in model peptides, with rate constants distributed over a range of more than two orders of magnitude. In addition, their pH min values vary widely. For most of the surface NH groups, pH min is lower than in model compounds and, for several, pH min is less than 1. These results indicate that the local environment of the surface peptide groups when the exchange event occurs is very different from that of extended peptides. Analysis based on consideration of an O-protonation mechanism for acid catalysis and of electrostatic effects on exchange kinetics further indicates (see the accompanying paper) that, in general, exchange of surface NH groups occurs from a conformation of the protein approximated by the crystal structure. The 1H-2H exchange rate constants were measured from 300 MHz nuclear magnetic resonance spectra in which assigned surface N1H resonances are resolved by the use of partially deuterated protein samples. A marked pH dependence of the chemical shifts observed in the pH range 1 to 4.5 for several surface NH groups reflects the titration of nearby carboxyl groups.

Amides↗
PubMed1985

Mechanism of surface peptide proton exchange in bovine pancreatic trypsin inhibitor. Salt effects and O-protonation.

The acid-catalyzed hydrogen exchange rate constants kH, and the base-catalyzed rate constants kOH, have been determined (in the preceding paper) for the 25 most rapidly exchanging NH groups of bovine pancreatic trypsin inhibitor. Most of these NH groups are at the protein-solvent interface. The correlation of kH, but not kOH, with the static accessibility and hydrogen bonding of the peptide carbonyl O atom indicates that the mechanism of acid catalysis in proteins involves O-protonation. Agreement between the ionic strength dependence observed for kH and kOH and the ionic strength dependence calculated for an O-protonation mechanism supports this conclusion. N-protonation for acid catalysis, as well as N-deprotonation for base catalysis, have traditionally been assumed in the mechanism of the chemical step in peptide amide proton exchange. A preference for the alternative O-protonation mechanism has far-reaching implications in the interpretation of protein hydrogen exchange kinetics. With an O-protonation mechanism, acid-catalyzed rates of surface NH groups are primarily a function of the average solvent accessibility of the carbonyl O atoms in the dynamic solution structure, while base-catalyzed rates of surface NH groups measure solvent accessibility of the peptide N. The relative dynamic accessibilities of peptide O atoms, as measured by relative values of kH (corrected for electrostatic effects), correlate with O static accessibilities in the crystal structure. A lower correlation of static accessibility of N atoms with kOH is observed for surface NH groups in peptide groups in which the carbonyl O is not hydrogen bonded. For some surface NH groups, the observed pH of minimum rate, pHmin, deviates widely from the pHmin of model compounds. This is explained as the combined result of electrostatic effects and of the differences in accessibility of the carbonyl O and N atoms that result in a change in the relative values of kH and kOH as compared to those of model peptides. A mechanism whereby exchange of interior sites is catalyzed by interactions of catalysis ions with protein surface atoms via charge transfer is suggested.

Amides↗
PubMed1985

Physician resource databank: numbers, distribution and activities of Canada's physicians.

The physician resource databank, compiled and maintained by the Canadian Medical Association (CMA), contains functional information from 41 599 of Canada's licensed physicians. The information was gathered from a 20-item questionnaire sent to 47 162 physicians. Of the total, 38 653 responses came from physicians who had completed their training and these were included in the analysis to produce a profile of the supply of physicians in Canada. The data from physicians younger than 35 years indicate some changes in the structure of the supply: 27% are women (compared with only about 9% of physicians older than 45 years).The implications of these statistics are not yet clear, but within the next decade the numbers in some specialties-surgery, anesthesia, obstetrics and gynecology, and radiology-may be too few to meet the demand as more than 20% of the current practitioners reach retirement age. Other findings are that [List: see text]

Age Factors↗
PubMed1985

A survey of postgraduate training for family practice.

The results of a survey of Canadian primary care physicians for the Canadian Medical Association (CMA's) Task Force on Education for the Provision of Primary Care Services are reported. Recent Canadian medical school graduates in primary care practice reported that the three major training routes (rotating and mixed internships and family medicine residencies) each prepared them differently for practice. The graduates of 2-year family medicine residencies were more satisfied with their preparation than were the graduates of the other major training routes. A 2- or 3-year family medicine residency was preferred by 50% of the respondents, although only 33% of them had actually taken one of these routes. There was considerable agreement in the respondents' assessments of the types of postgraduate education needed for primary care practice. The results of this survey were consistent with the recommendations in the final report of the CMA's task force.

Canada↗
PubMed1985

Rising from a chair. Influence of age and chair design.

We studied the effect of age on the act of rising from a standard armchair in a younger (means = 24 years) and an older (means = 75 years) group of healthy adult women. Rising from a standard armchair and an armchair specially designed for comfort in sitting of the elderly was studied in the older group to determine the influence of the special chair. We used electrogoniometry, EMG, and videotape analysis to record the activity for both groups. The older group placed their feet farther back and showed greater vastus lateralis muscle activity than did the younger group to rise from the standard chair. These results suggest that rising from the standard chair was more difficult for the older than for the younger group. In the special chair, the older subjects showed even more vastus lateralis muscle activity, greater knee flexion, and greater trunk forward lean. Rising from the special chair, therefore, appeared to be more difficult than rising from a standard chair; this finding suggests that both comfort and function must be considered in chair selection for certain groups.

Adult↗
PubMed1985

Plasma and serum concentrations of phenylbutazone and oxyphenbutazone in racing Thoroughbreds 24 hours after treatment with various dosage regimens.

The plasma and serum concentrations of phenylbutazone (PBZ) and oxyphenbutazone were measured in 158 Thoroughbred horses after various doses of PBZ wer given. All horses were competing or training at racetracks in various parts of the country. All horses used in the study had not been given PBZ 24 hours before they were placed on a specific dosage schedule. Samples were collected 24 hours after the last PBZ administration. Four grams of PBZ were given daily by stomach tube, paste, or tablet for 3 days. On day 4, 24 hours before sample collection, an IV dose of 2 g of PBZ was given, regardless of the dose and method of administration. The 24-hour PBZ plasma concentrations were 3.51, 6.13, and 6.40 micrograms/ml, respectively. After 2 g of PBZ was administered IV daily for 4 days, the plasma PBZ concentration was 4.16 g/ml; after a single 2-g IV administration, the serum concentration was 0.87 g/ml. Concentrations of oxyphenbutazone were 3.35 (stomach tube), 4.29 (paste), 3.60 (tablet), 3.65 (4-day IV), and 1.11 g/ml (single IV). A significant relationship was not found between the serum and the urinary concentrations at this 24-hour measurement. Split samples sent to various laboratories confirmed the stability of high-performance liquid chromatography as a method of analysis.

Administration, Oral↗
PubMed1983

Titratable effects of p-chloromercuriphenyl sulfonate, a thiol-attacking reagent, on glucocorticoid receptor binding.

Cytosol prepared from cultured AtT-20 mouse pituitary cells or mouse liver was treated with concentrations of p-chloromercuriphenyl sulfonate (PCMPS) which reduced but did not abolish receptor-binding activity. Scatchard analysis of triamcinolone acetonide binding to the treated cytosol showed that the PCMPS effect was caused by a reduction of binding affinity with little effect on the apparent binding site concentration. The effect on affinity was dose-dependent. Binding specificity appeared unaffected since the relative abilities of triamcinolone acetonide, dexamethasone, cortisol, progesterone, and corticosterone to compete with labeled triamcinolone were similar at various PCMPS concentrations which caused a progressive reduction of detectable cytosol binding. The PCMPS effect was reversible since cytosol treated with up to 200 microM PCMPS followed by dithiothreitol 15 min later showed nearly complete recovery of binding sites (62-100%). The possibility that several sulfhydryl groups were involved in this phenomenon was further explored in experiments using AtT-20 cytosol labeled with [3H]dexamethasone-mesylate, a glucocorticoid affinity label which binds covalently to sulfhydryl groups. Chromatography of dexamethasone-mesylate labeled receptor on a sulfhydryl affinity column resulted in binding, indicating that the receptor had at least two sulfhydryl groups, one bound to the mesylate moiety of the steroid and the other capable of binding to the affinity column.

4-Chloromercuribenzenesulfonate↗
PubMed1982

Hydrogen exchange and the dynamic structure of proteins.

In native proteins, buried, labile protons undergo isotope exchange with solvent hydrogens, but the kinetics of exchange are markedly slower than in unfolded polypeptides. This indicates that, whereas buried protein atoms are shielded from solvent, the protein fluctuates around the time average structure and occasionally exposes buried sites to solvent. Generally, hydrogen exchange studies are designed to characterize the nature of the fluctuations between conformational substates, to monitor the shift in conformational equilibria among protein substates due to ligand binding or other factors, or to monitor the major cooperative denaturation transition. In this article, we review the recent reports of hydrogen exchange in proteins, focusing on recent advances in methodology, especially with regard to the implications of the results for the mechanism of hydrogen exchange in folded proteins.

Crystallization↗
PubMed1981

One hospital's experience with a "Do not resuscitate" policy.

A "No not resuscitate" policy was instituted at McMaster University Medical Centre, Hamilton, in January 1979. Its objectives were to ensure that physicians decide on the appropriateness of resuscitation attempts before they might be needed; to have each physician consult his or her patients, or the families of incompetent patients, to determine their wishes concerning further treatment; and to provide legal protection of or physicians and the hospital in regard to the policy. To determine the effectiveness of the "Do not resuscitate" policy a questionnaire was sent to a sample of the professional staff of the hospital; the overall response rate was 87%. The respondents felt that a better way of informing hospital staff of the policy and its objectives was needed. However, the results of the questionnaire suggested that, on the whole, the policy was perceived as beneficial to both patients and physicians at the hospital.

Attitude of Health Personnel↗
PubMed1980

Extended-wear Hydrocurve and Sauflon contact lenses.

Fifty-six of 70 eyes selected for extended-wear lenses were successfully fitted with moderately hydrophilic (Hydrocurve II and Hydrocurve II-55) and highly hydrophilic (Sauflon) contact lenses. Thirty-two of 34 myopic eyes and 24 of 36 aphakic eyes were successfully fitted. The myopic eyes were followed up for two to 20 months and the aphakic eyes for two to 17 months. Ninety-one percent of all eyes achieved visual acuity better than or equal to 6.9 (20/30). Approximately 2.8 lenses per eye per year were required for success. The major complication was corneal edema (anoxic overwear); some of these cases responded to the fitting of looser, more hydrophilic lenses, frequent use of artificial tears, and increased blinking. There was no difference in the incidence of lens deposits between the moderately and highly hydrophilic lenses, and in only six eyes did lens deposits necessitate a lens change. There were no corneal ulcers in this study.

Adolescent↗