Oxidative Properties of the Skin: A Determinant for Nickel Diffusion
Jurij J. Hostýnek, Howard I. Maibach in Nickel and the Skin, 2019
Human skin features an acid mantle of pH 4 to 6 at the surface of the SC, which increases with depth to pH 7 at the juncture with live tissue (Öhman and Vahlquist, 1998). Determinants of this pH are protons, which gradually reach the surface of the skin, originating in the epidermis or as products of sebaceous gland activity. They stem from three classes of compounds: Amino acids, e.g., urocanic acid, pyrrolidone carboxylic acidAlpha-hydroxy acids, e.g., lactic and butyric acid, also present in sweatAcidic lipids, e.g., cholesteryl sulfate and free fatty acids, primarily oleic and linoleic (Elias, 1983; Lampe et al., 1983; Schurer and Elias, 1991).
Medical Countermeasures for Intoxication by Botulinum Neurotoxin
Brian J. Lukey, James A. Romano, Salem Harry in Chemical Warfare Agents, 2019
The inability of 3,4-DAP infusion to produce complete reversal of BoNT/A-mediated paralysis in the infusion studies may have resulted from the dose being too low. Higher doses could not be examined because the dose used was at the limit of aqueous solubility, indicating a need for a more potent K+ channel blocker. To achieve this aim, a series of aminopyridines, from both commercial and custom sources, were tested in the mouse phrenic nerve–hemidiaphragm assay by Adler and Borrell (unpublished observations). Table 14.1 shows a sample of the compounds tested and the percentage potentiation of twitch tension achieved. Test compounds were added at 100 µM after tensions were depressed to ~20% of control by exposure to 2 pM BoNT/A. Most compounds were weak or inactive in this assay, as exemplified by 6-aminopyridine-3-carboxylic acid. The remaining compounds, including those with single amine groups (2-aminopyridine [2-AP], 3-aminopyridine [3-AP], 4-aminopyridine [4-AP]) or two amine groups (2,3-diaminopyridine [2,3-DAP]), were all found to be less potent than 3,4-DAP. These results agree with those of Molgó et al. (1985) and indicate the difficulty of discovering aminopyridine analogs more potent than 3,4-DAP for blocking K+ channels at motor nerve terminals.
The Modification of Carboxyl Groups
Roger L. Lundblad, Claudia M. Noyes in Chemical Reagents for Protein Modification, 1984
Other approaches to the conversion of carboxylic acid functional groups to methyl or ethyl esters have been considered. Trialkyloxonium fluoroborate salts (Figure 2) have proved effective. Raftery and co-workers used triethyloxonium fluoroborate to modify the β-carboxyl groups of an aspartic residue essential for the enzymatic activity of lysoszyme.17,18 Paterson and Knowles19 used trimethyloxonium fluoroborate to determine the number of carboxyl groups in pepsin which are essential for catalytic activity. This article discusses in some depth the rigorous precautions necessary for the preparation of this reagent. This reagent is highly reactive and considerable care is required for its introduction into the reaction mixture containing protein. The reaction is performed at pH 5.0 (0.020 M sodium citrate, pH maintained at 5.0 with 2.5 M NaOH). These investigators also report the preparation of the 14C-labeled reagent from sodium methoxide and [14C] methyliodide.
Lipid–drug conjugates and associated carrier strategies for enhanced antiretroviral drug delivery
Published in Pharmaceutical Development and Technology, 2020
Funanani Takalani, Pradeep Kumar, Pierre P. D. Kondiah, Yahya E. Choonara, Viness Pillay
Fatty acids are made up of long aliphatic chains (4–28 carbon atoms) which may be saturated or unsaturated. Since they produce ATP (adenosine triphosphate) in large quantities during metabolism, they are regarded as important sources of fuel. Fatty acids are the most utilized lipid carriers because they grant high lipophilicity during the development of drug conjugation (Rajabi and Mousa 2016). They consist of a carboxylic acid and a hydrocarbon chain. Two ways through which fatty acids can be conjugated to drugs are: (i) through direct attachment of a drug to the carboxylic end of a lipid with hydroxyl or amino function to yield an ester or amide linkage (Zaro 2015). Herein, the most executed method is one whereby the -OH group is converted to a better leaving group by activating agents like carbodiimide. Then a drug containing an amine or alcohol group is added. (ii) Through keeping the carboxylic group free to allow fatty acids to bind serum albumin and gain recognition from transporters in the cell membrane while the drug attaches to the ω-atom that has been altered (Markovic et al. 2019). It is worth mentioning that fatty acids with longer chains (>14) result in higher absorption and circulation stability in contrast to shorter chains. Therefore, fatty acid chain length has impact on drug properties which may affect drug delivery (Zaro 2015).
Synthesis, characterization, antimicrobial and antimetastatic activity of silver nanoparticles synthesized from Ficus ingens leaf
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Doga Kavaz, Huzaifa Umar, Shafiu Shehu
The functional groups present in the synthesized nanoparticles were obtained from various spectrum peaks at different wavelengths as shown in Figure 7(b). At lower wavelength 500 cm−1, there was the presence of C–Br and C–Cl stretch that reveal alkyl halides. O–H bend at 910 cm−1 was the characteristic peak of carboxylic acid and C–H stretch at 1260 cm−1 revealed the presence of alkane. Also, N–O bend of nitro compound was shown around 1420 cm−1 and N–H bend of primary amines at 1610 cm−1. Finally, alcohol or phenol O–H stretch was also observed at 3350 cm−1. In similar studies, a clear diagnostics functional groups (i.e. O–H alcoholic/acid, and C–O–C) were displayed [32]. Moreover, the relative shift of these peak positions and intensity distribution in the IR of the two spectra (Figure 7(a,b)) indicates that different functional groups of the plant extract were probably involved in the AgNPs formation, and plays an important role in the capping and stabilization, which helps to avoid the AgNPs agglomeration.
Assessment of taste masking of captopril by ion-exchange resins using electronic gustatory system
Published in Pharmaceutical Development and Technology, 2020
Mellisa T. R. Chikukwa, Małgorzata Wesoly, Aleksandra B. Korzeniowska, Patrycja Ciosek-Skibinska, Roderick B. Walker, Sandile M. M. Khamanga
The FTIR spectra of pure CPT, IER, and the resinate are depicted in Figure 3. The CPT spectrum reveals the presence of bands characteristic of CPT due to functional groups in the structure of the molecule, viz. 1584.61 cm−1 representing the C–N amide bond, 1743 cm−1 representing the C = O carbonyl of the carboxylic acid (COOH) group and 2565 cm−1 representing the S–H thiol group (Kadin 1982). The characteristic bands for the IER are present at 3378.77, 1510.39, and 1612.58 cm−1 representing the N–H primary amine, C–N amide and the C = C alkene bonds, respectively. The characteristic signal bands for the S–H and C = O functional groups of CPT are absent in the FTIR spectrum of the resinate, indicating that complexation between the basic functional group of the IER and CPT had occurred and has been previously reported (Rajesh et al. 2015).