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Synthetic Nanoparticles for Anticancer Drugs
Published in Harishkumar Madhyastha, Durgesh Nandini Chauhan, Nanopharmaceuticals in Regenerative Medicine, 2022
To synthesise gold NPs, fucoside monomer-glycopolymer is first prepared using fucoside monomers (2-methacrylamidoethyl-2,3,4-tri-O-acetyl-a-L-fucopyranoside). The monomer is polymerised in dioxane via the classical method with 2-trimethylsilyl-ethanethiol as a chain transfer compound. Glycopolymer is produced by precipitating the per-acetylation polymer with ether. Pellets are collected through filtration and deprotected in NaOCH3/CH3OH (Jain & Das 2011). The second glycopolymer will partially sulphate in the presence of sulphur trioxide in the pyridine complex and dimethylformamide. They are converted to sodium bicarbonate to complete the sodium–sodium salt product (Shukla et al. 2005). A dialysis process using deionised water is performed to purify the obtained product. After synthesising the FM-glycopolymer, gold NPs are synthesise dusing NaBH4, which acts as a reducing agent.
Manual Methods for Protein/Peptide Sequence Analysis
Published in Ajit S. Bhown, Protein/Peptide Sequence Analysis: Current Methodologies, 1988
Low repetitive efficiency can be due to chemical or mechanical effects, that is, bad reagents/solvents or washout. This should not be confused with low initial yields, which are caused by chemical losses happening uniquely on Cycle 1, blocked peptide, or, most often, having less material than one thought. The most common cause of chemical inefficiency is oxidant in solvents, e.g., peroxide in EA exposed to air. This is why all such solvents should be protected from air and with scavengers such as ethanethiol. Reducing agents do not protect completely against photodecomposition products of alkyl halides, one reason chlorobutane and its relatives are not recommended, nor are they especially effective against heavy metals, the other common killer of sulfur chemistry. The thiourea added to the extracts minimizes all chemical problems from this point on, though it should not be used as a cure for impure or degraded solvents. Test all solvents and reagents (except PITC) periodically by exposing 100 pmol or so of PTH-Lys and Ala, along with an unreactive internal standard, to each of the solvents and reagents and note their relative recovery on HPLC; Lys is especially sensitive, as it possesses both a PTH and PTC functionality. Repetitive efficiency itself is classically assessed by sequencing myoglobin 12 to 15 cycles, calculating from the Val yields. In the absence of washout, efficiencies of 92 to 93% should be obtainable on 500 pmol, or only slightly lower than with the gas phase.
Chemical Leukoderma (Depigmentation)
Published in Francis N. Marzulli, Howard I. Maibach, Dermatotoxicology Methods: The Laboratory Worker’s Vade Mecum, 2019
Howard I. Maibach, Jorge R. Toro, Gerald A. Gellin, Leslie P. McCarty
In addition to the clinical observations, experimental studies have identified many compounds that cause hypomelanosis. Laundry ink containing p-cresol (CRE) produced depigmentation in CBA/J mice (Shelly, 1974). Bleehen et al. (1968) reported the results of thirty-three compounds tested in black guinea pigs; 12 compounds produced depigmentation. Very strong depigmenters were TBC, 4-isopropyl catechol (4IC), 4-methyl catechol (4MC), and catechol itself (CAT). Some produced definite but moderate hypopigmentation, among them, 3-isopropyl catechol (3IC), 3,5,-diisopropyl catechol (DIC), HY, 3-methyl catechol (3MC), and 3-methyl-5-tert-octyl catechol (MOC). Others produced definite but weak depigmentation: 3-terr-butyl 5-methyl catechol (BMC), 3i-ditertiary butyl catechol (DTBC), and 4-tert-octyl catechol (40C). Substitution in the 4 position confers greater activity than the same substituent in the 3 position; for example, 4-methyl catechol is more potent than 3-methyl catechol. Some, but not all, compounds containing a sulfhydryl group are capable of producing depigmentation. Beta-mercaptoethylamine hydrochloride (MEA) and N-(2-mercaptoethyl)dimethylamine hydrochloride (MEDA) were strong depigmenting agents. 3-Mercaptopropylamine hydrochloride and cystamine hydrochloride were weak to moderate depigmenters. Sulfanilic acid, cystamine, bis(2-amino-l-propyl)disulfide, 2-(N,N-dimethylamine)ethanethiol-S-acetate, 2-mercaptropropylamine hydrochloride, and alpha-mercaptoacetamide were weak depigmenters. Another study compared hydroquinone (HQ), MEA, and MEDA in black guinea pigs (Pathak et al., 1966). There is not as clear a pattern of structure-activity relationship among the thiols as there is with the phenols.
Systematic determination of the relationship between nanoparticle core diameter and toxicity for a series of structurally analogous gold nanoparticles in zebrafish
Published in Nanotoxicology, 2019
Lisa Truong, Tatiana Zaikova, Brandi L. Baldock, Michele Balik-Meisner, Kimberly To, David M. Reif, Zachary C. Kennedy, James E. Hutchison, Robert L. Tanguay
Only a few studies have been conducted wherein the surface ligand chemistry was held constant while the nanoparticle core diameter was systematically varied to specifically probe the size dependence. Pan et al. investigated a series of gold nanoparticles possessing sulfonated triphenylphosphine ligands and demonstrated the cytotoxicity was dependent on their size, where both the smaller (0.8 nm) and larger (15 nm) were less cytotoxic than the 1–2 nm particles (Pan et al. 2007). Yen et al. examined the cytotoxicity of gold nanoparticles containing no ligand shell in three diameter ranges: 2–4, 5–7 and 20–40 nm and found that cytotoxicity increased as the core diameters decreased (Yen, Hsu and Tsai, 2009). When gold nanoparticles of three-core size, 1.5, 4, and 14 nm were applied to Human Embryonic Stem Cells (hESCs), only 1.5 nm nanoparticles showed toxicity to hESC viability while the other two nanoparticles exhibited almost no toxic effects (Senut et al. 2016). In our work, comparing the toxicity of N,N,N-trimethylammonium ethanethiol-passivated 0.8, 1.5, and 15 nm diameter AuNPs using embryonic zebrafish, we found that the smaller AuNPs were more toxic when compared on an equal-mass concentration, but pointed out that comparing the toxicity based upon total surface area or number of particles would be more informative when considering the relative toxicity of these materials (Harper et al. 2011).
Isolation of a novel compound (MIMO2) from the methanolic extract of Moringa oleifera leaves: protective effects against vanadium-induced cytotoxity
Published in Drug and Chemical Toxicology, 2018
Olumayowa O. Igado, Jan Glaser, Mario Ramos-Tirado, Ezgi Eylül Bankoğlu, Foluso A. Atiba, Ulrike Holzgrabe, Helga Stopper, James O. Olopade
To obtain MIMO2 (which was the compound in MO), MIMO1 was demethylated. According to Node et al. (1979) 4.50 g (33.8 mmol) AlCl3 were dissolved in 2 mL of ethanethiol. 1.60 g (7.2 mmol) of MIMO1 were added and stirred for 2 hours. To enable better stirring, a small portion of CHCl3 was added. The resulting solution was poured into water, acidified with dilute HCl and extracted with CHCl3. The organic phase was then washed three times with brine, Na2SO4 solution and H2O, respectively. The chloroform phase was dried over MgSO4 and the solvent was evaporated, yielding 1.41 g (6.7 mmol, 93%) of butyl p-hydroxyphenyl acetate (MIMO2) as viscous yellowish sirup soluble in DMSO, but insoluble in H2O. NMR data were in accordance with the literature (Bevinakatti and Banerji 1992). MIMO2 was characterized to be a phenolic compound.
The efficacy and safety of amifostine for the acute radiation syndrome
Published in Expert Opinion on Drug Safety, 2019
Vijay K. Singh, Thomas M. Seed
The development of radioprotectors has been dominated by the investigation of sulfhydryl compounds, specifically aminothiols and phosphorothioates. Several mechanisms have been suggested for radioprotection by the use of sulfhydryl compounds, such as radiation-induced repair of DNA damage, free radical scavenging, genomic stabilization, modulation of cellular metabolism, modification of cell-cycle progression, augmentation of selective DNA repair enzymes, and scavenging of metals (Figure 2) [42,43]. The most meticulously studied, efficient, and valuable radioprotective thiols produced are WR-2721 (amifostine) and other phosphorothioates, such as WR-3689 – S-2-(3-methylaminopropylamino) ethylphosphorothioic acid and WR-151,327 – S-2-(3-methylaminopropylamino) propylphosphorothioic acid [26,27]. These phosphorylated compounds are prodrugs for the active free aminothiols, such as WR-1065 – [2-(3-aminopropylamino)ethanethiol] from WR-2721, WR-151326 – [3-(3-methylaminopropylamino)propanethiol] from WR-151327, and their disulfides generated in vivo. These free thiols can form disulfides, and WR-2721 can also be metabolized to cysteamine [44,45]. All of these WR-associated phosphorothioates exhibit effective, but distinct degrees of radioprotectiveness and drug toxicity/side effects when assessed using small animal rodent models [46]. Furthermore, different routes of administration have been documented as well [47]. The inadequately studied WR-159243 is well-tolerated agent that can be used orally soon before acute radiation exposure, while still attaining high levels of radioprotection (30 days survival, dose reduction factor (DRF) of ~1.3 and therapeutic index of ~7.5).