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Analysis of Essential Oils
Published in K. Hüsnü Can Başer, Gerhard Buchbauer, Handbook of Essential Oils, 2020
Adriana Arigò, Mariosimone Zoccali, Danilo Sciarrone, Peter Q. Tranchida, Paola Dugo, Luigi Mondello
The measurement of optical rotation, [α]D20, either dextrorotatory or laevorotatory, is also widely recognized. Optical activity is determined by using a polarimeter, with the angle of rotation depending on a series of parameters, such as oil nature, the length of the column through which the light passes, the applied wavelength, and the temperature. The degree and direction of rotation are of great importance for purity assessments, since they are related to the structures and the concentration of chiral molecules in the sample. Each optically active substance has its own specific rotation, as defined in Biot's law: where α is the optical rotation at a temperature T expressed in degrees Celsius, l is the optical path length in dm, λ is the wavelength, and c is the concentration in g/100 mL. It is worthy of note that a standard 100 mm tube is commonly used; in cases in which darker or lighter colored oils are analyzed, longer or shorter tubes are used, respectively, and the rotation should be extrapolated for a 100 mm-long tube. Moreover, prior to the measurement, the essential oil should be dried out with anhydrous sodium sulfate and filtered.
Amphetamines and Related Stimulants: Some Introductory Remarks
Published in John Caldwell, S. Joseph Mulé, Amphetamines and Related Stimulants: Chemical, Biological, Clinical, and Sociological Aspects, 2019
Amphetamine and most of its congeners of pharmacological interest have at least one chiral carbon center in their structure, the atom bearing the amino group, and are thus optically active. Exceptions to this are the phentermines, where the second α-methyl group in the side chain renders the carbon bearing the nitrogen nonchiral. In the ephedrines, the carbon bearing the side chain hydroxyl group is also chiral, creating a second optically active center. In all cases where optical activity (stereoisomerism) occurs, the compounds show marked stereoselectivity in their biological properties.
Conformational Changes in Nucleic Acids Modified by Chemical Carcinogens
Published in Philip L. Grover, Chemical Carcinogens and DNA, 2019
D. Grunberger, I. B. Weinstein
The second major feature of this model is that there is a stacking interaction between AAF and a base adjacent to the substituted G residue. Direct evidence for this in oligonucleotides has been obtained from both CD and PMR spectra.37–39 The CD results obtained with ApG are illustrated in Figure 3. At wavelengths greater than 290 nm, where most of the light absorption is due to AAF, the dichroism of AAF-modified ApG (A-Gaaf) is much greater than that of the modified monomer GMP (AAF-GMP). The optical activity in the 240 to 280 nm spectral region is also very pronounced. The intense bands in the spectra of this and other AAF-modified oligomers are probably the result of intramolecular interaction between the transition dipoles of fluorene and the adjacent base residue. It is unlikely that they reflect intermolecular interactions because the concentrations of the dimers are relatively low (10−5M), there is no salt other than buffer in the solutions, and the spectra are concentration independent over the 10−4 to 10−5M range. A reversible temperature dependence of the CD spectrum of ApGAAf, and of several other AAF-modified oligomers, is observed when the solvent is changed from H2O to MeOH (Figures 4 and 5).38 These properties are also characteristic of stacking interactions.
Gold nanostars-diagnosis, bioimaging and biomedical applications
Published in Drug Metabolism Reviews, 2020
Seyyed Mojtaba Mousavi, Maryam Zarei, Seyyed Alireza Hashemi, Seeram Ramakrishna, Wei-Hung Chiang, Chin Wei Lai, Ahmad Gholami
The researchers have proven that appropriate activities of GNS arise from surface plasmon resonance (SPR) which is an intrinsic feature of them. By applying light to GNS at the determined wavelengths, electrons commence vibrating in resonance situations with the light’s frequency that is because of the fundamental interaction between the electromagnetic field of the original light and the conduction electrons of gold nanoparticles (Wu et al. 2019). The SPR provides interesting optical properties like high scattering cross-surfaces and absorption coefficient for GNS. Many factors like local dielectric areas, size, and shape of GNS can affect the SPR wavelengths. It can be mentioned that GNS have the ability to be modified by the surface with oligonucleotides, peptides, proteins, and some other compounds while they can maintain their optical properties in high quality. This surface modification of GNS can lead to superior targeting properties and also enhances the efficiency in imaging (Oyelere et al. 2007; Dam et al. 2015). Due to the low toxicity and high biocapability of GNS, they can widely be utilized in chemical and biological applications especially in biosensing and imaging (Murphy et al. 2008; Cho et al. 2010; Niu et al. 2015; Mulder et al. 2019). The morphology of GNS grants them suitable physicochemical and optical activities, which can be controlled by simple form modifications. The researchers investigated the optical activity of GNS and they proposed that GNS have the potential to be utilized in both Raman imaging and PTT and thus multi-operational theranostics (Gao et al. 2017).
Pharmaceutical potential of quantum dots
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Swati Jha, Prateek Mathur, Suman Ramteke, Narendra Kumar Jain
QD’s make it possible to track cell processes for longer periods of time and shed new light on molecular interactions as they are much more resistant to degradation than other optical imaging probes. Real time imaging is the most unique feature of QDs.QDs are basically nanocrystals, so they provide good contrast for imaging with an electron microscope as scattering increases.QDs have size-tunable emission (from UV to IR).QDs show prolonged fluorescence as compared to conventional dyes.QDs exhibit increased optical activity with innumerable avenues of applications in biotechnology and life sciences.The extremely small size imparts QDs great versatility by allowing them to be injected into many environments including liquid mixtures, fabrics, and polymer matrices.
Thermal, structural, antimicrobial, and physicochemical characterisation of thyme essential oil encapsulated in β- and γ-cyclodextrin
Published in Journal of Microencapsulation, 2022
Jasim Ahmed, Mehrajfatema Z. Mulla, Hassan Al-Attar, Shaikhah AlZuwayed, Mohammed Ejaz, Sarah Al-Jassar, Harsha Jacob, Linu Thomas, Noor Al-Ruwaih, Antony Joseph
β-cyclodextrin (BCD) and γ-cyclodextrin (GCD) (Cavamax W7 and Cavamax W8; 99% purity) were procured from Wacker Chemie AG (Munich, Germany). The molecular weights of Cavamax W7 and Cavamax W8 are 1135 and 1297 g/mol, respectively. Thyme oil was procured from Sigma-Aldrich (St. Louis, MO, USA). According to the supplier, T. vulgaris and/or Thymus zygis were the sources of the oil with France origins. The density, optical activity, refractive index, and boiling point of the oil are 0.917 g/mL at 25 C, [α]20/D − 1°, n20/D 1.502, and 195 °C, respectively. Ethanol was purchased from Fisher Scientific (Loughborough, LE, UK).