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Candidate Substances, Research Background, and Biological Roles
Published in Shojiro Inoué, Biology of Sleep Substances, 2020
In the course of investigations on bromine intoxication in human patients, Yanagisawa and Yoshikawa118 found that, in addition to exogenous bromine, a bromine-containing organic substance occurred physiologically in both CSF and blood. This substance was isolated from a large amount of pooled human CSF and finally identified as 1-methyl-heptyl-γ-bromoacetoacetate (γ-Br or MHBAA).119 Subsequent studies revealed that γ-Br (0.1 to 5 mg i.v.) selectively promoted PS in encephale isolé cats.120 This will be described in detail in Chapters 2 and 7.
Halogen Labeled Compounds (F, Br, At, Cl) *
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
The chemistry of bromine is somewhat similar to that of fluorine and the physical properties of Br such as van der Waals radius, polarizability, and electronegativity are in between that of fluorine and iodine as shown in Table 1. The reactivity of Br2 is, in general, much milder than F2, but greater than I2. The binding strength of the C—Br bond is approximately 15 kcal/mol stronger than that of the C—I bond. Thus brominated compounds are less susceptible to in vivo dehalogenation than the corresponding iodinated compounds. Unlike iodide, bromide does not accumulate in the thyroid.
Radiotracers For Nonimaging Studies: II
Published in Garimella V. S. Rayudu, Lelio G. Colombetti, Radiotracers for Medical Applications, 2019
L. Rao Chervu, Shanta Chervu, M. Donald Blaufox
This is an analytical modality which is particularly appealing since no radioactive biomedical tracers are involved in the procedures.168 The irradiation of the tissue or target containing the element of interest is carried out with a low-energy X-ray or gamma-photon beam, e.g., Americium 241 (60 keV) source or filtered X-ray tube beams. The characteristic resultant X-rays are resolved by high resolution detectors. These high-resolution low-noise Si (Li) or high purity germanium detectors coupled with multichannel analyzers offer excellent means of energy resolution of characteristic X-rays differing by 1 or 2 keV. These techniques offer levels of detectability of tracer elements of Z greater than 30 on the order of 0.5 to 1.0 ppm in in vitro, and 100 to 200 ppm in in vivo measurements. Biomedical applications include the quantitation of bromine at diagnostic levels in serum and urine, determination of bromide space in man, and measurement of the iodine concentration and its spatial distribution in the thyroid gland.65, 179, 180
The improved antiviral activities of amino-modified chitosan derivatives on Newcastle virus
Published in Drug and Chemical Toxicology, 2021
Xiaofei He, Ronge Xing, Song Liu, Yukun Qin, Kecheng Li, Huahua Yu, Pengcheng Li
In the FT-IR spectra (Li et al. 2012, Meng et al. 2012) (Figure 2), a broad band at 3200–3400 cm−1 was attributed to the H-bonded OH stretch and the H-bonded NH stretches. The bands at 2800–2900 cm−1 correspond to aliphatic CH stretching. The C=O stretching vibration appeared at approximately 1650 cm−1 while the bending vibration of the free amino group appeared at 1590 cm−1 (Subhapradha et al. 2013). Moreover, the bands at 1400 cm−1, 1350 cm−1, and 1000 cm−1 correspond to the stretching vibration of C–N, bending vibration of C–H and stretching vibration of C–O, respectively (Xia et al. 2013). All of these revealed that the primary structure of chitosan was not damaged during the synthesis. In addition, the band appeared at 1600–1400 cm−1 and 880–650 cm−1 suggested the successful introduction of phthalic acyl. Element analysis result showed that the substitution degree of bromine was 54.17%.
Halogen gas exposure: toxic effects on the parturient
Published in Toxicology Mechanisms and Methods, 2021
Dylan R. Addis, James A. Lambert, David A. Ford, Tamas Jilling, Sadis Matalon
Today the non-medical applications of the halogens are myriad with bromine having continued value in photographic development, dyes, purification agents, disinfectants, and as a flame retardant. Chlorine remains commonly utilized for water sanitation and is employed broadly for numerous industrial and medicinal processes. Several reports indicate that bromine is a more effective disinfectant than chlorine resulting in an increased utilization of bromine for drinking water purification (Floyd et al. 1976; Coulliette et al. 2010; World Health Organization 2018). To facilitate this demand global production of bromine exceeds 500 000 tons annually with the United States, China, and Israel (where the Dead Sea serves as an important source of bromine) responsible for the majority of production (The International Bromine Council 2019). Chlorine is produced on a larger scale with a global estimation of 58 million metric tons of chlorine and 62 million metric tons of sodium hydroxide (a co-product of chlorine) produced annually (World Chlorine Council 2012).
Halogen bonding in halocarbon-protein complexes and computational tools for rational drug design
Published in Expert Opinion on Drug Discovery, 2019
Paulo J. Costa, Rafael Nunes, Diogo Vila-Viçosa
Boeckler and co-workers developed a strategy based on the design of halogen-enriched fragment libraries (HEFLibs) which exploits halogen bonding for lead discovery [46]. They screened a HEFLib and performed structure-guided design to develop substituted 2-(aminomethyl)-4-ethynyl-6-iodophenols that stabilize p53 cancer mutation Y220C [101]. In the design of the HEFLib, QM calculations (MP2/TZVPP) along with spherical scans (Section 5) were used to, in advance, discover that the carbonyl oxygen of Leu145 was targetable for halogen bonding in addition to hydrogen bonding. The compounds were experimentally evaluated and the most promising lead (compound 8) showed evidence, by X-ray crystallography, of a halogen bond with the main chain oxygen of Leu145 (Figure 4, left). Substituting the iodine by bromine or chlorine resulted in a decrease in activity (20-fold and 4-fold, respectively), thus reinforcing the importance of halogen bonding. Further lead optimization afforded inhibitor PhiKan5196 (9), the most potent p53 Y220C stabilizer identified at that time, that also binds via a halogen bond (Figure 4, right). Curiously, the same p53 Y220C mutant was used to study the bioisosteric replacement of a halogen by an ethynyl group [102]. This chemical group, mimicking aromatic systems and being a weak hydrogen bond donor, possesses an area of positive charge at the tip of the C-H bond analogous to what is found in C-X bonds. Nonetheless, 13-fold loss in affinity was observed upon substitution which was explained, using QM calculations, by a larger extent of the ethynyl moiety when compared with iodine which cannot be accommodated by the p53-Y220C binding site. The HEFLibs strategy, initially applied to p53 mutant stabilizers, was very recently revisited and extended [47] by introducing a huge diversity of binding motifs aiming at increasing their applicability to various targets. In this work, the authors showed how to create new libraries with diverse properties (chemical groups, shape, σ-hole magnitude). Each halogen-substituted aromatic ring is treated as the central element for molecular similarity assessment, the remainder substituents being treated as modifiers or substituents connected to the central core. This eventually enabled to highlight the influence of the halogenated moiety environment in binding while decreasing the influence of the most distant molecular features. The information concerning charges, hydrogen bond donors/acceptors and linkers, together with a prediction of VS,max (using VmaxPred [44], see Section 2) is stored. A final HEFLib comprising 198 fragments was acquired, imposing a hard limit of $5/mg on the price, excluding compounds without aromatic halogens and larger than 20 heavy atoms, and performing a prior solubility assessment. Therefore, the HEFLib contained affordable and highly soluble compounds, thus increasing the probability of reaching high ligand concentrations in vitro.