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Biomedical subjects

R L Petersen

Publications and source records attributed to R L Petersen.

12 recordsLinked to original sources
PubMed1999

Influenza and pneumococcal vaccine receipt in older persons with chronic disease: a population-based study.

OBJECTIVE: To identify factors associated with receipt of the pneumococcal and influenza vaccines among community-dwelling older persons with chronic disease. METHODS: A population-based sample of urban and rural Iowa adults age 65 years and older with one or more self-reported target medical conditions were interviewed by telephone. Information was obtained on aspects of health care access, which were examined as potential determinants of receipt of recommended vaccines. RESULTS: A total of 787 interviews were completed (response rate = 68%; completion rate for screened, eligible subjects = 91%). Two-thirds (n = 531, 68%) reported influenza vaccination in the last year, and one-half (51%, n = 393) reported ever receiving the pneumococcal vaccine. Both vaccines were received at recommended intervals by 347 subjects (44%). Multivariable logistic regression identified the following factors independently associated with receipt of both vaccines: age 70 or greater (OR = 1.64, CI95 = 1.15, 2.32); married (OR = 1.41, CI95 = 1.03, 1.92); self-owned residence (OR = 0.57, CI95 = 0.33, 0.97); working (OR = 2.94, CI95 = 1.38, 6.18); increased number of target medical conditions (OR = 1.3 for each, CI95 = 1.09, 1.54); current prescription medication (OR = 2.04, CI95 = 1.32, 3.14); and a physician visit in the last year (OR = 2.53, CI95 = 1.52-4.19). Receipt of the vaccines was unrelated to geographic location in a rural area. CONCLUSIONS: Despite their proven safety and efficacy, many persons with at least two indications to receive either vaccine remain unvaccinated. Among the elderly with chronic disease, predisposing and need factors were independently associated with receipt of both vaccines. Enabling factors assessed appeared less important in this population. Targeting of the elderly and those with chronic disease to receive recommended vaccines is needed to adequately protect these populations at risk.

Aged↗
PubMed1979

A novel form of vitamin B-12 and its derivatives.

A new isomeric form of cobalamins is reported. The conversion of cobalamin to cobalamin (the new form) is achieved by substituting the benzimidazole base by a less bulky group like H2O or CN- and modest thermal treatment. The back conversion of adenosylcobalamin to the corresponding regular form occurs in the "base-off" form at room temperature. It seems that the corrin ring becomes quite flexible in the "base-off" form and the freer axial movement of the cobalt atom flips the corrin ring into a different conformation. The change in conformation is borne out by subtle changes in the proton magnetic resonances on the corrin ring and the base, and very marked variation in the emission Mössbauer spectra. The latter is indicative of appreciable changes in the spatial conformation in the immediate vicinity of the central metal atom. The ultraviolet-visible and infrared spectra of cobalamin are indistinguishable from those of its corresponding regular form. The new conformational isomeric species is present as an impurity in all commercially available cobalamins (including pharmaceutical preparations). It raises the question whether the cobalamins' constitute the real biologically active anti-anemic factor in humans.

Anemia↗
PubMed1979

Magnetic resonance studies of the spatial arrangement of glucose-6-phosphate and chromium (III)-adenosine diphosphate at the catalytic site of hexokinase.

The interaction of CrADP, an exchange-inert paramagnetic analogue of Mg-ADP, with yeast hexokinase has been studied by measuring the effects of CrADP on the longitudinal nuclear relaxation rate (1/T1) of the protons of water and the protons and phosphorus atom of enzyme-bound glucose-6-P. The paramagnetic effect of CrADP on 1/T1 of water protons is enhanced upon complexation with the enzyme. Titrations measuring this paramagnetic effect at several enzyme concentrations in the presence of glucose-6-P yielded a characteristic enhancement factor for 1/T1 of water protons and the dissociation constant of CrADP from the ternary enzyme . ADPCr . glucose-6-P complex. The latter value (2 mM) is similar to that obtained from kinetic inhibition studies (Danenberg and Cleland [1975]. Biochemistry. 14:28). The presence of glucose-6-P increased the enhancement of the water relaxation rate by enzyme-bound CrADP, suggesting the formation of an enzyme . CrADP . glucose-6-P complex. The existence of such a complex was confirmed by the observation of a paramagnetic effect of enzyme-bound CrADP on the l/T1 of the 31P-nucleus and protons of enzyme-bound glucose-6-P. From the paramagnetic effects of enzyme-bound CrADP on the relaxation rates of the 31P-nucleus and the carbon-bound protons of glucose-6-P in the enzyme . ADPCr . glucose-6-P complex, using the correlation time of approximately 0.7 ns, determined from the magnetic field-dependence of 1/T1 of water protons over the range 24.3-360 MHz, a Cr3+ to phosphorus distance of 6.6 +/- 0.7 A and Cr3+ to alpha- and beta-anomeric proton distances of 8.9 and 9.7 A were calculated. These results imply the absence of a direct coordination of the phosphoryl group of glucose-6-P by the nucleotide-bound metal on hexokinase but indicate van der Waals contact between a phosphoryl oxygen of glucose-6-P and the hydration sphere of the nucleotide-bound metal. The distances are consistent with a model that assumes molecular contact between the phosphorus of glucose-6-P and a beta-phosphoryl oxygen of ADP suggesting an associative phosphoryl transfer. Because after phosphorylation of ADP, the metal ion is coordinated to the transferred phosphoryl group, the overall migration of the phosphoryl group during the phosphoryl transfer is approximately 3.6 A toward the nucleotide-bound metal. Little or no catalysis of phosphoryl transfer from glucose-6-P to alpha, beta-bidentate or beta-monodentate CrADP ( less than or equal to 0.05% of the rate found with MgADP) occurred in the presence of hexokinase, as monitored by glucose formation in a coupled assay system using glucose oxidase and peroxidase. The ability of beta, gamma-bidentate CrATP to act as a substrate (Danenberg and Cleland [1975].

Adenosine Triphosphate↗
PubMed1978

The relative electron affinities of the alpha and beta chains of oxyhaemoglobin as a function of pH and added inositol hexaphosphate. An electron spin resonance study.

Exposure of aqueous glasses of oxyhaemoglobin to 60Co gamma-rays at 77K results in electron addition to the FeO2 unit, the ESR spectrum for the alpha-chain electron adduct being well separated from that for the beta-chain. The relative yields of these two centres has been measured in the pH range 4.5 to 8.5, with or without added inositol hexaphosphate. We find that, in the absence of inositol hexaphosphate, the yield of beta-chain adduct is almost equal to that of the alpha-chains in the pH 4--5 region, but these rapidly diverge with increasing pH, the beta-yield increasing and the alpha-yield decreasing. After a plateau in the pH 6--8 region, the yield of beta-chain adduct decreases, but that of the alpha-chain adduct remains constant. In the presence of an excess of inositol hexaphosphate the pH change for the beta-adduct remains, but at low pH values the yield of the alpha-adduct is much greater than that of the beta-adduct. This constraint is removed with a pK of approx. 7.7 and at high pH values the yield of the beta-adduct is once again greater than that of the alpha-adduct. These results are significant in that they suggest that the electron affinities of the alpha and beta chains in oxyhaemoglobin are a function of pH, with that of the beta-chains being greater than that of the alpha-chains in the neutral region. Also inositol hexaphosphate clearly binds to one or both chains, and this has the effect of reversing the relative electron affinities of the two chains.

Electron Spin Resonance Spectroscopy↗
PubMed1978

Electron capture at the iron-oxygen centre in single crystals of oxymyoglobin studied by electron spin resonance spectroscopy.

Exposure of single crystals of oxy-myoglobin to 60Co gamma-rays at 77 K results in electron addition to the Fe-O2 units. The resulting ESR spectrum has been analysed to give the principal values and directions for the g-tensor of this unit. The results suggest that the dioxygen ligand is strongly tilted, the direction of tilt being close to one of the bisectors of the N-Fe-N bond angles. Possible reasons for this orientation are discussed.

Chemical Phenomena↗
PubMed1978

Electron addition to the active site of Cancer magister haemocyanins. An ESR study of cu(II) centres after gamma-radiolysis.

Exposure of aqueous glasses of Cancer magister haemocyanin to 60Co gamma-rays at 77 K results in a novel paramagnetic centre with ESR features showing hyperfine coupling to one strongly coupled 63/65 Cu nucleus and possibly one weakly interacting 63/65 Cu nucleus. Addition of electron scavengers showed that this centre is formed by electron addition. It is suggested that addition occurs at Cu2+-O2-Cu2+ units to give Cu2+-O2Cu+ centres. If this is correct, then electron-transfer between the two copper ions is slow or non-existent, possibly indicating that they are inequivalent. The centre is unstable, the signals being lost irreversibly on heating to approx. 270 K. The g parallel and A parallel (63/65Cu) data place this centre into the type I classification.

Animals↗
PubMed1977

Determination of ionization state by resonance Raman spectroscopy Sulfonamide binding to carbonic anhydrase.

Resonance Raman (RR) spectroscopy has been used to study the ionization state of the sulfonamide, 4'-sulfamylphenyl-2-azo-7-acetamido-1-hydroxynaphthalene-3,-6-disulfonate (Neoprontosil), bound to carbonic anhydrase. The correlation of effects of pH and deuteration on the spectra of model compounds with these effects on the Neoprotosil spectrum allows us to assign spectral bands in the 900-1000 and 100-1200 cm-1 regions to the SO2NH2 group. Large shifts in these bands occur upon ionization of the sulfonamide. On the basis of the positions of bands in the enzyme complex, it was determined that the sulfonamide was bound to the enzyme as SO2NH2, rather than as SO2NH-. Rates of association and dissociation and the dissociation equilibrium constant were measured as a function of pH. The rate behavior for Neoprontosil is consistent with that observed for other sulfonamides and kdissoc/kassoc = kdissoc, suggesting a one-step binding mechanism. Since RR spectroscopy establishes that the final ionization state of the sulfonamide in the enzyme complex is SO2NH2, protonated sulfonamide must bind directly to basic form of the enzyme. These conclusions suggest that sulfonamides form "outer-space" complexes with metal at the enzyme active site.

Animals↗
PubMed1975

Resonance Raman investigation of an enzyme-inhibitor complex.

The resonance Raman spectrum has been recorded for two different binary complexes formed between 2-carboxy-2'-hydroxy-5'-sulfoformazylbenzene (zincon) and liver alcohol dehydrogenase. The shifts in the zincon spectrum upon complexation with enzyme in one complex are similar to those in model compounds containing azo or formazyl linkages upon complexation of these with zinc. The results are interpreted in terms of complexation of zincon to a zinc atom at the enzyme active site. Since zincon is a coenzyme competitive inhibitor, it is probably bound at or near the coenzyme binding site; the results of this study, therefore, are useful in understanding the chemistry of zinc at the enzyme active site.

Alcohol Oxidoreductases↗