Fluorescence contrast and threshold limit: implications for photodynamic diagnosis of basal cell carcinoma

This study was designed to evaluate what application time of delta-5-aminolaevulinic acid (ALA) results in highest contrast between tumour and normal skin, in the interval 1-4 h, when using photodynamic diagnosis (PDD) of basal cell carcinomas (BCC) located on the face. Moreover, a value of the demarcation limit has been derived based on the fluorescence variation in normal skin adjacent to the tumour. Forty patients were included in the study, randomly allocated to four different groups with varying ALA application time in the range 1-4 h. The contrast, defined as the ratio between the fluorescence intensity in ALA-treated tumour tissue and normal skin, was calculated for each patient, and the mean values in each group were evaluated as a function of ALA application time. In addition, the fluorescence intensity variation in ALA-treated normal skin adjacent to the tumour was assessed. The results from this study show a peak of the mean contrast values after 3 h ALA application, but due to large interpatient variation, the mean contrast did not differ significantly in the interval 2-4 h. After 2 h ALA application, the fluorescence intensity variation in the normal ALA-treated skin was found to be at a maximum, which suggests that 2 h ALA application is not preferable when using PDD. Based on data of the fluorescence variation in ALA-treated normal skin after 3 and 4 h ALA application, a tolerance interval was calculated implying that values above 1.4 times the mean normal fluorescence indicate an abnormal condition. This tolerance limit agrees well with results obtained in a former study.     

Separation of oxidized and deamidated human growth hormone variants by isocratic reversed-phase high-performance liquid chromatography.

Reversed-phase high-performance liquid chromatography (RP-HPLC) was utilized for the separation of recombinant human growth hormone (hGH) variants on a C18 silica column at 55 degrees C using an isocratic mobile phase which contained 27% 1-propanol in a 25 mM potassium phosphate buffer, pH 6.5. Three of the obtained peaks were characterized by tryptic mapping and mass spectrometry; two of the peaks were found to contain oxidized hGH (dioxy Met14/Met125 and Met125 sulfoxide) while the third contained a deamidated form (Asn149-->Asp149 or Asn152-->Asp152). Compared to the European Pharmacopoeia RP-HPLC method of hGH analysis, this new method gives two additional peaks and a 50% reduction in the analysis time.     

Conformational analysis of hydroxymatairesinol in aqueous solution with molecular dynamics

Molecular dynamics simulations were performed on the naturally occuring lignan hydroxymatairesinol (HMR) using the GROMACS software. The aim of this study was to explore the conformational behavior of HMR in aqueous solution adopting the TIP4P model. The topology of HMR was constructed by hand and HMR was modeled with the OPLS‐AA force field implemented in GROMACS. The five torsional angles in HMR were properly analyzed during the simulations. Correlations through certain patterns were observed between the angles. The determining property for the conformation preferred in aqueous solution was found to be the dipole moment and not the lowest energy in gas phase. The solvation effects on HMR was also studied by quantum chemical calculations applying the COnductorlike Screening MOdel (COSMO), the results of which were compared with results from a previous study using the Polarized Continuum Model (PCM). In the present work, COSMO was found to give more credible relative energies than PCM. © 2009 Wiley Periodicals, Inc., J Comput Chem, 2009     

A skew normal dilation on the numerical range of an operator

Simple facts about the Poincaré-Neumann double layer potential are used in the construction of a normal dilation, on the numerical range of an arbitrary Hilbert space operator. Recent and old ideas in the theory of the numerical range are unified by this framework. A couple of mapping results for the numerical range are derived.Revised version: 15 July 2002First author partially supported by the National Science Foundation Grant DMS 0100367, Second author supported by STINT, The Swedish Foundation for International Cooperation in Research and Higher Education.     

Glutamic acid 181 is negatively charged in the bathorhodopsin photointermediate of visual rhodopsin

Assignment of the protonation state of the residue Glu-181 is important to our understanding of the primary event, activation processes and wavelength selection in rhodopsin. Despite extensive study, there is no general agreement on the protonation state of this residue in the literature. Electronic assignment is complicated by the location of Glu-181 near the nodal point in the electrostatic charge shift that accompanies excitation of the chromophore into the low-lying, strongly allowed ππ* state. Thus, the charge on this residue is effectively hidden from electronic spectroscopy. This situation is resolved in bathorhodopsin, because photoisomerization of the chromophore places Glu-181 well within the region of negative charge shift following excitation. We demonstrate that Glu-181 is negatively charged in bathorhodopsin on the basis of the shift in the batho absorption maxima at 10 K [λ(max) band (native) = 544 ± 2 nm, λ(max) band (E181Q) = 556 ± 3 nm] and the decrease in the λ(max) band oscillator strength (0.069 ± 0.004) of E181Q relative to that of the native protein. Because the primary event in rhodopsin does not include a proton translocation or disruption of the hydrogen-bonding network within the binding pocket, we may conclude that the Glu-181 residue in rhodopsin is also charged.     

Electroosmotic perfusion of tissue: sampling the extracellular space and quantitative assessment of membrane-bound enzyme activity in organotypic hippocampal slice cultures

This review covers recent advances in sampling fluid from the extracellular space of brain tissue by electroosmosis (EO). Two techniques, EO sampling with a single fused-silica capillary and EO push–pull perfusion, have been developed. These tools were used to investigate the function of membrane-bound enzymes with outward-facing active sites, or ectoenzymes, in modulating the activity of the neuropeptides leu-enkephalin and galanin in organotypic-hippocampal-slice cultures (OHSCs). In addition, the approach was used to determine the endogenous concentration of a thiol, cysteamine, in OHSCs. We have also investigated the degradation of coenzyme A in the extracellular space. The approach provides information on ectoenzyme activity, including Michaelis constants, in tissue, which, as far as we are aware, has not been done before. On the basis of computational evidence, EO push–pull perfusion can distinguish ectoenzyme activity with a ~100 μm spatial resolution, which is important for studies of enzyme kinetics in adjacent regions of the rat hippocampus. Graphical Abstract

Schematics for the one-probe electroosmotic sampling (EO sampling, left) and two-probe electroosmotic push-pull perfusion techniques (EOPPP, right). An external electric field drives fluid flow in the direction indicated by the arrows. HBSS - Hanks Balanced Salt Solution.     

Generation of a triplet diradical from a donor-acceptor cross conjugate upon acid-induced electron transfer

Enhancement of the electron acceptor ability of a para-quinodiimine unit by double protonation leads to the proton-induced intramolecular electron transfer from the donor unit to the cross-conjugated acceptor, giving rise to ground state triplet diradical reversibly.