Lasers in Medicine: Healing with Light
Suzanne Amador Kane, Boris A. Gelman in Introduction to Physics in Modern Medicine, 2020
The penetration depth is determined by the extinction coefficient, which characterizes the degree of absorption by individual molecules and concentration of the absorbing molecules by the equation: where ε is the extinction coefficient and c is concentration. The value of the extinction coefficient depends on the wavelength of light being absorbed. This means that the more absorbers present along a given pathway, the shorter the distance light travels before being absorbed – higher concentrations lead to shorter penetration depths. Similarly, the penetration depth is shorter if the extinction coefficient of the material is greater; both depend on wavelength. For example, for green light, blood-filled tissue absorbs light in a shorter distance than tissue containing little blood. Similarly, the lens of the eye has a long penetration depth for visible light. By contrast, visible wavelengths have short penetration depths in the retina, which has a high concentration of strongly absorbing visual pigments.
Biomedical Applications in Probing Deep Tissue Using Mid-Infrared Supercontinuum Optical Biopsy
Lingyan Shi, Robert R. Alfano in Deep Imaging in Tissue and Biomedical Materials, 2017
In the MIR range, molecular species exhibit fundamental absorption bands with large extinction coefficients thus MIR spectroscopy potentially provides extremely sensitive chemical analysis. A molar extinction coefficient (or molar absorptivity coefficient) is defined by the Beer-Lambert law and is a measure of the relative light absorption of a particular vibrational mode of a molecular species normalized to the molar concentration of the absorbing species. Knowledge of the molar extinction coefficient allows quantification of the amount of the molecular species present. The response to MIR spectroscopy is collected as a spectrum, of the material concerned, which is a plot of intensity of MIR radiation versus wavelength and shows the uptake of radiation intensity at particular wavelengths due to vibrational absorption of the material which is characteristic of the molecular structure of the material.
Lipid Peroxidation
Robert A. Greenwald in CRC Handbook of Methods for Oxygen Radical Research, 2018
Malondialdehyde is one of the products of lipid peroxidation which appears to be produced in relatively constant proportion to lipid peroxidation. It is therefore a good indicator of the rate of lipid peroxidation, especially in vitro. The thiobarbituric acid (TBA) assay for malondialdehyde is accomplished by mixing the sample with a TBA reagent consisting of 0.375% TBA and 15% trichloroacetic acid in 0.25 N HCl. The TBA is dissolved in the HCl first, and then the trichloroacetic acid is added. The reagent is generally stable but may precipitate upon storage, in which case the reagent is heated and stirred until the TBA redissolves. The reaction mixture of sample and TBA reagent is placed in a boiling water bath for 15 min, cooled, and centrifuged, and the optical density of the clear supernatant is recorded at 532 nm. An absorption spectrum should be obtained periodically to assure that there are no interfering aldehydes, which would be detected by an absorption maximum at other wavelengths. A standard curve can be obtained with malondialdehyde tetraethylacetal using the same assay procedure. We obtain an extinction coefficient of 1.56 × 105M−1 cm−1.
Graphene oxide influence in soil bacteria is dose dependent and changes at osmotic stress: growth variation, oxidative damage, antioxidant response, and plant growth promotion traits of a Rhizobium strain
Published in Nanotoxicology, 2022
Tiago Lopes, Paulo Cardoso, Diana Matos, Ricardo Rocha, Adília Pires, Paula Marques, Etelvina Figueira
Glutathione was determined using the method described by Rahman, Kode, and Biswas (2006). In a 2 mL microtube, 100 μL of supernatant was mixed with 2 μL 2-vinylpyridine (1:10 (v/v)) (diluted in KPE buffer (0.1 M of potassium phosphate buffer, 5 mM EDTA, pH 7.5) and incubated for 1 h at room temperature. After, 6 μL triethanolamine (1:6 (v/v)) (diluted in KPE buffer) was added and incubated for more than 10 min at room temperature. To 33.3 μL of the mixture from each microtube, 193 μL phosphate buffer (0.1 M potassium phosphate, 5 mM EDTA buffer, pH 7.5), 40 μL glutathione reductase (3.33 U/mL) with 1.68 mM DTNB (5,5-dithiobis-(2-nitrobenzoic acid)) and 20 μL 2.64 mM NADPH were added, and the absorbance measured at 412 nm for 20 min with 30 s intervals. The extinction coefficient of TNB (Ɛ = 13600 M−1 cm−1) was used. Results were expressed in nanomole per million cells (nmol/M cells).
Methotrexate induced mitochondrial injury and cytochrome c release in rat liver hepatocytes
Published in Drug and Chemical Toxicology, 2018
Abdullah Al Maruf, Peter J. O’Brien, Parvaneh Naserzadeh, Rozhina Fathian, Ahmad Salimi, Jalal Pourahmad
H2O2 was measured in hepatocytes by adding FOX1 reagent. The FOX1 reagent consisted of 25 mM sulfuric acid, 250 μM ferrous ammonium sulfate, 100 μM xylenol orange and 100 mM sorbitol. Fifty microliters of hepatocytes suspension were added to 950 μL of the FOX1 reagent and incubated for 30 min at room temperature. Samples were then spectrophotometrically analyzed at 560 nm using an extinction coefficient 2.35 × 105 M−1 cm−1 (Ou & Wolff, 1996). H2O2 values were expressed as nmol/106 cells.
Synthesis and characterisation of a new benzamide-containing nitrobenzoxadiazole as a GSTP1-1 inhibitor endowed with high stability to metabolic hydrolysis
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Veronica Di Paolo, Chiara Fulci, Dante Rotili, Francesca Sciarretta, Alessia Lucidi, Blasco Morozzo della Rocca, Anastasia De Luca, Antonio Rosato, Luigi Quintieri, Anna Maria Caccuri
The compound was first dissolved in 100% DMSO and then subjected to scalar dilution in buffer A (0.1 M potassium phosphate, pH 7.4, containing 0.1 mM EDTA and 0.1% (v/v) Triton X-100). The maximum solubility of these solutions was evaluated by recording the absorbance maxima (∼430 nm) and using a molar extinction coefficient calculated at the same wavelength, using diluted standard solutions prepared in buffer A (concentration range: 4–40 µM). The extinction coefficient was obtained by linear regression analysis of a plot of the maximum absorbance vs. compound concentration.
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