PubMed · 935833
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B A Ambler, R W Proctor. 1976. Rod involvement in peripheral color processing.. https://doi.org/10.1111/j.1467-9450.1976.tb00223.x
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OBJECTIVES: The objectives were to measure the color change of varied shades of dental resin composites after polymerization, and to determine the correlation among the polymerization color change and the changes in color parameters after polymerization. METHODS: Eight light-curing resin composites, a total of 41 shades, were studied. Color of specimens (1 mm in thickness) was measured on a reflection spectrophotometer before and after polymerization over a white background. Changes in color (Delta E*(ab)), and color parameters (Delta L*, Delta C*(ab), Delta a*, and Delta b*: value after polymerization - value before polymerization) were calculated. RESULTS: The range of changes in each shade of resin composites was 1.1-7.9 for color (Delta E*(ab)), -7.5 to 2.3 for Delta L*, -6.8 to 3.1 for Delta C*(ab), -0.9 to 1.2 for Delta a*, and -6.8 to 3.1 for Delta b*. Delta E*(ab), Delta L*, Delta C*(ab), Delta a*, and Delta b* were influenced by the brand and shade of resin composites, and there was a significant interaction between two independent variables (p < 0.05). On the basis of the multiple regression analysis, in which Delta E*(ab) after polymerization was set as a dependent variable and Delta L*, Delta C*(ab), Delta a* and Delta b* as independent variables, multiple correlation coefficient (r) was 0.842 and the included predictors were Delta L* [standardized partial correlation coefficient (beta) = -0.760] and Delta C*(ab) (beta = -0.715). This result indicated that the polymerization changes in color and color parameters were varied by the brand and shade of resin composites, and the polymerization color change was caused by the changes in lightness and chroma with the similar power of influence.
Secondary metabolites called norlignans are produced in the xylem of Cryptomeria japonica D. Don. Several norlignans have roles in the defense of sapwood against microbial invasion and in the coloration of heartwood. The biosynthetic pathway of norlignans is largely unknown. Norlignans have been reported to accumulate in the sapwood during the drying of C. japonica logs. To search for genes encoding enzymes that catalyze the synthesis of norlignans, we carried out suppression subtractive hybridization using the fresh sapwood of a felled log and the drying sapwood in which a norlignan, agatharesinol, accumulated. A total of 1050 expressed sequence tags were obtained from the subtracted cDNA library, and these were assembled into 146 contigs and 361 singletons. Of these 507 unique sequences, 263 were functionally classified into 12 categories. "Metabolism" was the largest category, with 23% (61) of classified sequences. Twenty-six sequences that encode 16 enzymes were assigned to "secondary metabolism." Expression analysis of 15 genes related to "secondary metabolism" revealed that 12 of these genes had transcripts that were induced during the sapwood drying process. Of the 12 genes, 10 encoded enzymes that use aromatic compounds as substrates. In addition, 58 sequences representing 22 defense-related proteins were found. Our subtraction library should be a useful source for isolating genes encoding proteins involved in secondary metabolism including norlignan biosynthesis and defense in C. japonica xylem.
Wavelength-dependent one- and two-color photon echo peak shift spectroscopy was performed on the chlorophyll Qy band of trimeric photosystem I from Thermosynechococcus elongatus. Sub-100 fs energy transfer steps were observed in addition to longer time scales previously measured by others. In the main PSI absorption peak (675-700 nm), the peak shift decays more slowly with increasing wavelength, implying that energy transfer between pigments of similar excitation energy is slower for pigments with lower site energies. In the far-red region (715 nm), the decay of the peak shift is more rapid and is complete by 1 ps, a consequence of the strong electron-phonon coupling present in this spectral region. Two-color photon echo peak shift data show strong excitonic coupling between pigments absorbing at 675 nm and those absorbing at 700 nm. The one- and two-color peak shifts were simulated using the previously developed energy transfer model (J. Phys. Chem. B 2002, 106, 10251; Biophysical Journal 2003, 85, 140). The simulations agree well with the experimental data. Two-color photon echo peak shift is shown to be far more sensitive to variations in the molecular Hamiltonian than one-color photon echo peak shift spectroscopy.