Examples of Hartmann-Hahn match conditions for CP/MAS between two half-integer quadrupolar nuclei.

Hartmann-Hahn match conditions for n2 --> M2 CP/MAS between two quadrupolar nuclei, spin-lock signal as a function of effective nutation frequency, and the correlation of effective nutation frequency and radiofrequency field strength are reported for three samples: sodium diborate (Na2B4O7), aluminum boride (AlB2), and lithiump aluminate (LiAlO2). Radiofrequency field strengths used for CP/MAS are both greater and less than the sample spinning speed of 10 kHz, resulting in the observation of both zero-quantum and double-quantum matches, which have signals of opposite sign. The match conditions for Na2B4O7 are as expected from published theory and CP/MAS experiments on spins 12 and n2 (n = 3 or 5) with quadrupole frequencies (omegaQ) large compared to the radiofrequency field strength of the CP contact pulse, consisting mainly of sideband matches at one and two times the sample spinning frequency, and the correlation of effective nutation frequency and radiofrequency field strength supports the conclusion that omegaQ is large for both 11B and 23Na. Aluminum-27 in AlB2 may have either small or intermediate omegaQ, and 7Li in LiAlO2 is proposed to have intermediate omegaQ in relation to the radiofrequency field strength, and both have curves of the spin-lock signal as a function of effective nutation frequency with central minima, differing from those of the nuclei with large omegaQ. The sign of the CP/MAS signal for AlB2 and LiAlO2 appears to vary with the CP field strengths for the two nuclei so that positive or negative signals cannot be consistently correlated with zero- or double-quantum matches. However, it is possible to assign at least some of the matches as close to integral multiples of the sample spinning frequency, and some of these are matches at greater than two times the sample spinning frequency.

Becoming a part of the community: implementing a public health vision in student health services.

Principles from public health and community health nursing provide an approach to student health services that enhances interdisciplinary collaboration and advocacy for access to care. Staff participation in the campus community requires administrative support, both in philosophy and in making outreach activities accessible to staff. Student health services at University of Maine's Cutler Health Center in Orono is implementing outreach and community involvement as ongoing aspects of the college health nursing role. Increased collaboration, visibility of nurses on campus, and improved community assessment and intervention are among the outcomes observed during the past 2 years. This article describes the principles that guide this approach and shares some community involvement experiences, including the response to a student suicide attempt, social support for students after a residence hall fire, and case management/consultation services.

Quantification of the disorder in network-modified silicate glasses.

Local order in silicate glasses has been observed by many experimental techniques to be similar to that in crystalline materials. Details of the intermediate-range order are more elusive, but essential for understanding the lack of long-range symmetry in glasses and the effect of composition on glass structure. Two-dimensional 17O dynamic-angle-spinning nuclear magnetic resonance experiments reveal intermediate-range order in the distribution of inter-tetrahedral (Si-O-Si) bond angles and a high degree of order in the disposition of oxygen atoms around the network-modifying cations.

Public health nurse salaries: associations with nurse, agency, and community characteristics.

This study applied an economic framework to the analysis of public health nurse (PHN) salaries, assessing their relationships to nurse qualifications, agency resources, community economic base, and area competition for the nurse supply. Data were obtained through interviews with 125 Ohio health departments and from various state and local reports. Associations between salaries and explanatory variables were analyzed through correlations and stepwise regression models. The PHN salaries were significantly lower and more compressed than salaries for nurses in area hospitals. Agency and community characteristics were more important than nurse education and experience in explaining salary variations. Maximum PHN salary attainable was significantly related to level of health department funding and community unemployment rate. Health departments in rural locations paid lower salaries at both minimum and maximum levels. Evidence suggested the presence of entry-level wage competition by health departments with both area hospitals and other community nursing agencies. Each 1% increase in minimum hospital nurse salaries was linked to a 0.66% increase in PHN salaries. Findings support the need to improve competitive positions of health departments as nurse shortages intensify.

Proton NMR assignments and regular backbone structure of bovine pancreatic ribonuclease A in aqueous solution.

Proton NMR assignments have been made for 121 of the 124 residues of bovine pancreatic ribonuclease A (RNase A). During the first stage of assignment, COSY and relayed COSY data were used to identify 40 amino acid spin systems belonging to alanine, valine, threonine, isoleucine, and serine residues. Approximately 60 other NH-alpha CH-beta CH systems were also identified but not assigned to specific amino acid type. NOESY data then were used to connect sequentially neighboring spin systems; approximately 475 of the possible 700 resonances in RNase A were assigned in this way. Our assignments agree with those for 20 residues assigned previously [Hahn, U., & Rüterjans, H. (1985) Eur. J. Biochem. 152, 481-491]. Additional NOESY correlations were used to identify regular backbone structure elements in RNase A, which are very similar to those observed in X-ray crystallographic studies [Wlodawer, A., Borkakoti, N., Moss, D. S., & Howlin, B. (1986) Acta Crystallogr. B42, 379-387].

Effect of calcium (II) and magnesium (II) ions on the 18-23 gamma-carboxyglutamic acid containing cyclic peptide loop of bovine prothrombin. An AMBER molecular mechanics study.

The effect of calcium (II) and magnesium (II) ions on the conformation of the 18-23 cyclic peptide loop of bovine prothrombin are investigated by the molecular mechanics program AMBER (Assisted Model Building with Energy Refinement). The work is an extension of an earlier paper (Eastman et al., Int. J. Peptide Protein Res. 27, 1986, 530-553) that employed the program ECEPP (Empirical Conformational Energy Program for Peptides). In the absence of either metal ion, or in the presence of either one Ca(II) or one Mg(II) ion, the lowest-energy forms found by AMBER have the Gla21-Pro22 peptide bond in a trans conformation. In the presence of two Ca(II) or Mg(II) ions, the loop form of lowest energy is decidedly cis. The coordination about the Ca(II) and Mg(II) ions is different in both the single and double metal cases. In addition, the peptide chains that emerge from the loop are oriented parallel to each other in the lowest-energy complex with two Ca(II) ions, but are not parallel in the lowest-energy complex with two Mg(II) ions.

Conformation of the 18-23 loop region of bovine prothrombin in the absence and presence of a model Ca2+ ion. An energy minimization study.

The conformation of the cyclic peptide Ac-Cys-Leu-Gla-Gla-Pro-Cys-NHMe, representing the 18-23 disulfide loop of bovine prothrombin, was studied by energy minimization with the ECEPP (Empirical Conformational Energy Program for Peptides) algorithm. Parameters for charge and geometry for the gamma-carboxyglutamic acid (Gla) residue were obtained for inclusion in the ECEPP data set. Construction of the 18-23 cyclic peptide, for which no crystal structure is available, was carried out by using a scheme that took advantage of the constraints imposed by the requirement of disulfide ring closure and utilized known low-energy structures of single residues and dipeptides. Both cis and trans isomers about the Gla 21-Pro 22 peptide bond were considered. The lowest-energy conformation found for the isolated 18-23 cyclic peptide with arbitrary reduction of the charge on the Gla residues (to simulate hydration roughly) is a trans form, differing in energy by 11 kcal-mol-1 from the lowest-energy cis form. However, when the energy calculation includes one model Ca2+ ion, X2+, introduced at a fixed distance of 2.3 A from a single oxygen atom of either of the side-chain carboxyl groups of Gla with the C delta-O-X2+ bond angle fixed at one of three values, the lowest-energy cis conformation is about 1 kcal-mol-1 lower in energy than the lowest-energy trans conformation; i.e. the two structures have similar energies. In these structures, four oxygen atoms, two from each Gla side-chain, approach the model Ca2+ ion closely, in a manner similar to that seen in crystals of calcium alpha-ethylmalonate (Zell, A., Einspahr, H. & Bugg, C.E. (1985) Biochemistry 24, 533-537). It appears that the binding of Ca2+ to the 18-23 cyclic peptide may alter the equilibrium between cis and trans structures such that the fraction of cis isomers is greater in the presence of Ca2+.