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- Forsum, Urban, et al.
(författare)
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An international study of the inter-observer variation between the interpretations of vaginal smear criteria of Bacterial Vaginosis
- 2002
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Ingår i: APMIS. - : Wiley. - 1600-0463 .- 0903-4641. ; 110:11, s. 811-818
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Tidskriftsartikel (refereegranskat)abstract
- An international workshop on vaginal smear-based diagnosis of bacterial vaginosis was organized where 13 investigators scoring 258 slides with smears from vaginal fluid. Interobserver reproducibility of interpretations of Nugent scores, Hay/Ison scores and wet smear scores for the diagnosis of bacterial vaginosis was shown to be high. Detailed analysis of individual scoring results however indicated that basic standards of quality control to ensure robust individual readings of slides must be adhered to.
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| 4. |
- Tuttle, Tell, 1980, et al.
(författare)
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Analysis of the NMR spin-spin coupling mechanism across a H-bond: Nature of the H-bond in proteins
- 2004
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:3, s. 1115-1129
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Tidskriftsartikel (refereegranskat)abstract
- The NMR spin-spin coupling constants (SSCCs) across the H-bond in proteins are sensitive to the electronic structure of the H-bonded system, i.e., the N-(HO)-O-...=C group in proteins. The spin-spin coupling mechanism across the H-bond involves a strong electric field effect, steric exchange interactions, and some weak covalent effects (transfer of electronic charge). The electric field effect is reflected by one-orbital contributions to the SSCC and can be tested with the help of probe charges. A negative charge opposite to the N-H bond leads to increased polarization of the N-H bond, a larger contact density at the N nucleus, and a stronger FC coupling mechanism for those SSCCs involving the N nucleus. Similarly, a positive charge opposite to the O=C bond, distorts the O density into the direction of the external charge and in this way decreases the spin density at the O nucleus. All SSCCs across the H-bond depend primarily on the electric field effect and two-orbital steric exchange interactions. The lone pair contributions to the Fermi contact term of (2h)J(ON) (and to a lesser extent (3h)J(CN)) provide a direct measure on possible covalent contributions in the form of charge-transfer interactions. According to calculated charge-transfer values and lone-pair contributions to SSCC (2h)J(ON), the covalent contribution to the H-bond is rather small (less than 15% at 1.9 Angstrom for a bending angle beta(COH) of 120degrees). The zeroth-order density and the spin-spin coupling mechanism, which depends largely on the first-order spin density, both describe the H-bond as being electrostatic rather than covalent. The electric field effect largely determines the geometrical dependence of the SSCCs of a hydrogen-bonded system.
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