Reactivities of Amino Acids and Proteins with Iodine
Erwin Regoeczi in Iodine-Labeled Plasma Proteins, 2019
A similar interchain cross-linking function is envisaged287 for ortho-linked tyrosines, first described by Andersen288 in resilin, a rubber-like protein that occurs in some elastic ligaments in arthropods. The structure (in proper chemical notation 2,2 ′ -dihydroxy-5,5 ′ -di-(2-carboxy-2- aminoethyl)biphenyl), already encountered briefly in Chapter 3, Section II. C.3.a, can also be readily synthesized in vitro from tyrosine either by a peroxidase-H2O2 reaction,289 or by tetranitromethane.242 However, model studies with p-cresol242 suggest that tetranitro- methane may also give rise to the formation of Pummerer’s ketone:290
General toxicology
Timbrell John in Study Toxicology Through Questions, 2017
For a compound to bioaccumulate it should be lipid soluble rather than water soluble. For example, the pesticide DDT will bioaccumulate in organisms exposed to it as it dissolves in the fat in adipose tissue. Second, the compound should be resistant to metabolism and therefore poorly excreted so that it is eliminated slowly from the organism. For example, polybrominated biphenyl compounds, such as those which contaminated livestock and people in Michigan in 1973, are very resistant to metabolism, are eliminated extremely slowly and so have very long half-lives. Continued exposure to such compounds will therefore result in accumulation in fat tissue.
Percutaneous Absorption of Hazardous Substances from Soil and Water
Francis N. Marzulli, Howard I. Maibach in Dermatotoxicology Methods: The Laboratory Worker’s Vade Mecum, 2019
Table 5 gives the in vitro and in vivo percutaneous absorption of polychlorinated biphenyl (PCBs) (Wester et al., 1993a). As with the other organic chemicals with high log/3, receptor fluid accumulation in vitro was essentially nil. In vitro, PCB showed some accumulation in skin. In vivo, PCB percutaneous absorption for both aroclor 1242 and 1254 was (a) high, ranging from 14 to 21% and (b) generally independent of formulation vehicle. Thus PCBs have a strong affinity for skin and are relatively easily absorbed into and through skin.
Biphenyl-induced cytotoxicity is mediated by an increase in intracellular Zn2+
Published in Drug and Chemical Toxicology, 2019
Masamichi Ae, Naohiro Imura, Tomoko Inubushi, Shin Abe, Bekki Yusuke, Mayumi Sugimoto, Norio Kamemura
Biphenyl was dissolved in dimethyl sulfoxide (DMSO). Various concentrations of biphenyl (3–300 mM in 1 μL DMSO) were added to cell suspensions (1 mL per test tube) and incubated at 36–37 °C for 1 or 3 h. The concentration of 300 μM biphenyl resulted in limited dissolution in the cell suspensions; therefore, cells were treated with biphenyl concentrations of less than 300 μM in subsequent experiments. To examine the effects of DTPA, TPEN, and H2O2, each agent was individually added to the suspension 1 min before applying biphenyl. We chose to use a concentration of 100 μM H2O2 because Matsui et al. (2010) showed that 100 μM H2O2 increases intracellular Zn2+ levels, but not rates of cell death, in thymocytes. Therefore, 100 μM H2O2 is an optimal concentration for examining the increased sensitivity to oxidative stress induced by biphenyl in thymocytes. The final concentration of DMSO as a solvent was 0.1% or less. Incubation with DMSO at 0.3% or less did not affect the viability of rat thymocytes. Therefore, 0.1% DMSO was chosen as the control group.
Concentration dependence of human and mouse aryl hydrocarbon receptor responsiveness to polychlorinated biphenyl exposures: Implications for aroclor mixtures
Published in Xenobiotica, 2019
Hongxue Shi, Josiah E. Hardesty, Jian Jin, Kimberly Z. Head, K. Cameron Falkner, Matthew C. Cave, Russell Allen Prough
PCBs are polyhalogenated aromatic hydrocarbons and consist of up to 10 chlorine atoms attached to a biphenyl ring. PCBs were manufactured as mixtures (US tradename Aroclor) and sold by the percentage of chlorine in the mix. For example, Aroclor 1254 is 54% chlorine by mass, while Aroclor 1260 is 60% chlorinated. Of the 209 theoretical PCB congeners, approximately 130 were present in commercial PCB mixtures. PCB mixtures were used in a variety of industrial applications, such as insulating agents for electrical transformers. Approximately 1.3 million tons were produced worldwide before PCBs were banned (Ockenden et al., 2003). The primary routes of human PCB exposure are ingestion of contaminated food (Schecter et al., 2003) or breast milk, and inhalation of contaminated air (Ampleman et al., 2015). PCB metabolism varies considerably with low molecular weight PCBs being metabolized at a higher rate than the more heavily chlorinated PCBs. This leads to bioaccumulation patterns in adipose that greatly favor retention of the more highly chlorinated congeners being similar to those present in Aroclor 1260. However, there is an important exception. Aroclor 1260 is not believed to contain significant amounts of DL PCBs (Battelle Memorial Institute, 2012; Wahlang et al., 2014a; Wahlang et al., 2014b).
Inhibitors of type II transmembrane serine proteases in the treatment of diseases of the respiratory tract – A review of patent literature
Published in Expert Opinion on Therapeutic Patents, 2020
Alexandre Murza, Sébastien P. Dion, Pierre-Luc Boudreault, Antoine Désilets, Richard Leduc, Éric Marsault
Matriptase has been associated for a long time with cancers. In particular, overexpression of matriptase or under-expression of its natural inhibitor Hepatocyte growth factor Activator Inhibitor 1 (HAI-1) has been reported in multiple cancers of epithelial tissues [89]. In an effort to discover a new treatment for carcinoma progression associated with matriptase [90], Lin and coworkers screened 69 small molecules tested at 75 µM for inhibitory activity against the recombinant enzyme (US6677377) [91]. Further Ki determination was reported on 15 compounds possessing >95% inhibition. Seven biphenyl derivatives bearing positively charged amidine groups separated by linkers of variable lengths emerged as the most interesting compounds in this series Figure 7A. Kis for matriptase range from 191 nM (13) to >10,000 nM while few compounds were also assessed for their ability to inhibit UPA and thrombin, with Kis in the µM range.
Related Knowledge Centers
- Aromatic Compound
- Chirality
- Emulsion
- Functional Group
- Fungicide
- Organic Compound
- Phenyl Group
- Polychlorinated Biphenyl
- Chemical Formula
- Optical Brightener