This study presents a mathematical model, which expresses the absorbance of a photosynthetic sample as a non-linear polynomial of selected reference absorbance. The non-linearity is explained by inhomogeneities of a product of pigment concentration and light path length in the sample. The quadratic term of the polynomial reflects the extent of inhomogeneities, and the cubic term is related to deviation of the product distribution from a symmetric one. The model was tested by measurements of suspension of unstacked tobacco thylakoid membranes of different chlorophyll concentrations in cuvettes of different thicknesses. The absorbance was calculated from the diffuse transmittance and reflectance of sample, illuminated by perpendicular collimated light. The evaluated quantity was a sensitivity defined as the relative difference between the sample absorbance and the reference absorbance to the reference absorbance. The non-linearity of sample absorbance was demonstrated by a characteristic deviation of the sensitivity spectrum from a constant value. The absorbance non-linearity decreased on an increase of the product of pigment concentration and cuvette thickness. The model suggests that the sieve and detour effects influence the absorbance in a similar way. The model may be of interest in modeling of leaf or canopy optics including light absorption and scattering.
- MeSH
- Chlorophyll metabolism MeSH
- Photosynthesis radiation effects MeSH
- Plant Leaves physiology radiation effects MeSH
- Pigmentation radiation effects MeSH
- Light MeSH
- Nicotiana physiology radiation effects MeSH
- Remote Sensing Technology MeSH
- Models, Theoretical * MeSH
- Thylakoids radiation effects MeSH
- Publication type
- Journal Article MeSH
- Keywords
- ozářená moč, biologický dozimetr, biologický indikátor, barevný indikátor, síran železnatý,
- MeSH
- Absorption MeSH
- Urinalysis MeSH
- Biomarkers MeSH
- Radiation Dosage MeSH
- Humans MeSH
- Urine * MeSH
- Radiometry MeSH
- Radiotherapy * adverse effects MeSH
- Sulfates * diagnostic use MeSH
- Spectrophotometry MeSH
- Statistics as Topic MeSH
- Ferrous Compounds MeSH
- Check Tag
- Humans MeSH
The authors present a study of the fluorescence and absorbance transients occurring in whole cells of purple nonsulfur bacterium Rhodobacter sphaeroides on the millisecond timescale under pulsed actinic illumination. The fluorescence induction curve is interpreted in terms of combination of effects of redox changes in the reaction center and the membrane potential. The results of this study support the view that the membrane potential act predominantly to increase the fluorescence yield. Advantages of the pulsed actinic illumination for study of the operation of the electron transport chain in vivo are discussed.
- MeSH
- Absorption radiation effects MeSH
- Spectrometry, Fluorescence MeSH
- Carotenoids metabolism MeSH
- Kinetics MeSH
- Membrane Potentials radiation effects MeSH
- Oxidation-Reduction radiation effects MeSH
- Rhodobacter sphaeroides cytology metabolism radiation effects MeSH
- Light MeSH
- Publication type
- Journal Article MeSH
Efficient absorbance detection of a low-volume chromatography peak is a difficult task. In this work, an improved design of the fused silica capillary flow cell for absorbance detection in microcolumn liquid chromatography is described. The cell was fabricated from 0.15 mm I. D. fused silica capillary and silica optical fibres. Optical fibres were fully integrated into the cell design and enabled a convenient and effective connection of the cell with the light source and light detector (265 nm UV LED and photodiode in this work). Manufactured cells covered the range of physical lengths 3.1-9.9 mm (55-175 nL) and were used without any focusing optics and slits. Baseline noise was typically below 0.05 mAU and the effective optical path determined in the experiments was 83-97% of the cell's physical length. The level of stray (parasitic) light indicated by a 1% deviation from linearity at 1.7 AU was 0.08% only. The proposed cell design was found to be moderately susceptible to the refractive index change (20-35 mAU baseline change in 5-95% (v/v) gradient of acetonitrile or methanol in a mixture with water, G index up to 4 AU·s/RIU). Manufactured cells were finally applied for absorbance detection of components of test the mixture eluted off 0.3 mm I. D. microcolumn. 9.9 mm cell (175 nL) with an effective optical path of 8.9 mm exhibited contribution to the broadening of chromatography peak comparable with commercial 6 mm (80 nL) rectangular flow cell.
- MeSH
- Chromatography, Liquid MeSH
- Commerce MeSH
- Optical Fibers * MeSH
- Silicon Dioxide * MeSH
- Water MeSH
- Publication type
- Journal Article MeSH
- MeSH
- Antioxidants pharmacology chemistry MeSH
- Spectrometry, Fluorescence MeSH
- Carbolines pharmacology chemistry MeSH
- Thiobarbituric Acid Reactive Substances analysis MeSH
- Serum Albumin, Bovine chemistry drug effects MeSH
- Serum Albumin MeSH
- Cattle MeSH
- Spectrophotometry, Ultraviolet MeSH
- Animals MeSH
- Check Tag
- Cattle MeSH
- Animals MeSH
