He Hypobromous acid (HOBr, HBrO) is an inorganic acid produced by the oxidation of the bromide anion (Br-). The addition of bromine to water gives hydrobromic acid (HBr) and hypobromous acid (HOBr) through a disproportionation reaction.
Br2 + H2O = HOBr + HBr
Hypobromous acid is a very weak, somewhat unstable acid, existing as a dilute solution at room temperature. It is produced in warm-blooded vertebrate organisms (including humans) by the action of the peroxidase enzyme of eosinophils.
The discovery that hypobromous acid can regulate the activity of collagen IV has attracted great attention.
- Formulas
| Hypobromous acid | |
| Formulas | HOBr HBrO |
- CAS number : 13517-11-8
2D structure
Hypobromous acid
3D structure
Hypobromous acid. Molecular model of solid spheres
Hypobromous acid. Molecular model of bars and spheres
characteristics
Physical and chemical properties
| Hypobromous acid | |
| Appearance | Yellow solids |
| Molecular weight: | 96.911 g / mol |
| Boiling point: | 20-25 ° C |
| Density: | 2.470 g / cm 3 |
| Acidity (pKa) | 8.65 |
- The chemical and physical properties of hypobromous acid are similar to those of other hypohalites.
- It is presented as a dilute solution at room temperature.
- Hypobromite solids are yellow in color and have a peculiar aromatic odor.
- It is a strong bactericide and water disinfectant.
- It has a pKa of 8.65 and partially dissociates in water to pH 7.
Applications
- Hypobromous acid (HOBr) is used as a bleaching agent, oxidant, deodorant, and disinfectant, because of its ability to kill the cells of many pathogens.
- It is used by the textile industry as a bleaching agent and a desiccator.
- It is also used in whirlpools and spas as a germicidal agent.
Biomolecular interactions
Bromine is ubiquitous in animals as ionic bromide (Br-), but until recently, its essential function was not known.
Recent research has shown that bromine is essential for basement membrane architecture and tissue development.
The enzyme Peroxidasin uses HOBr to form crosslinks in sulfilimine that is cross-linked in the basement membrane collagen IV scaffolds.
Hypobromous acid is produced in warm-blooded vertebrate organisms by the action of the peroxidase enzyme of the eosinophils (EPO).
EPO generates HOBr from H 2 O 2 and Br- in the presence of a plasma concentration of Cl-.
Myeloperoxidase (MPO), from monocytes and neutrophils, generates hypochlorous acid (HOCl) from H 2 O 2 and Cl-.
Canine myeloperoxidase. Molecular model of solid tapes
EPO and MPO play an important role in host defense mechanisms against pathogens, using HOBr and HOCl respectively.
Neutrophils during phagocytosis
The MPO / H2O2 / Cl- system in the presence of Br- also generates HOBr by the reaction of the HOCl formed with Br-. More than a potent oxidant, HOBr is a powerful electrophile.
The plasma concentration of Br- is more than 1000 times lower than that of the chloride anion (Cl-).
Consequently, the endogenous production of HOBr is also lower compared to HOCl.
However, HOBr is significantly more reactive than HOCl when the oxidability of the compounds studied is not relevant, so the reactivity of HOBr may be more associated with its electrophilic strength than with its oxidizing power (Ximenes, Morgon & de Souza, 2015).
Although its redox potential is lower than that of HOCl, HOBr reacts with amino acids faster than HOCl.
The tyrosine ring halogenation by HOBr is 5000 times faster than that of HOCl.
Tyrosine. Molecular model of wires
HOBr also reacts with the nucleobases of nucleosides and DNA.
Double DNA helix. Molecular model of solid spheres
2-deoxycytidine, adenine and guanine, generate 5-bromo-2'-deoxycytidine, 8-bromoadenine and 8-bromoguanine in EPO / H2O2 / Br- and MPO / H2O2 / Cl- / Br- systems (Suzuki, Kitabatake and Koide, 2016).
McCall, et al. (2014) have shown that Br is a cofactor required for the formation of cross-linked sulphilimine catalyzed by the peroxidase enzyme, a posttranslational modification essential for collagen IV architecture of basement membranes and tissue development.
Collagen molecule IV (COL4A1). Molecular model of solid tapes
Basal membranes are specialized extracellular matrices that are key mediators of signal transduction and mechanical support of epithelial cells.
Basal membrane, extracellular matrix, epithelium, endothelium and connective tissue
Basal membranes define the architecture of epithelial tissue and facilitate repair of tissue after injury, among other functions.
Embedded within the basement membrane is a collagen scaffold IV crosslinked with sulfilimine, which gives functionality to the matrix in the multicellular tissues of all animals.
Collagen IV scaffolds provide mechanical strength, serve as a ligand for integrins and other cell surface receptors, and interact with growth factors to establish signaling gradients.
Sulfilimine (sulfimide) is a chemical compound containing a double sulfur to nitrogen bond.
Sulfilimine bonds stabilize the collagen IV strands found in the extracellular matrix.
These bonds covalently bind methionine residues 93 (Met93) and hydroxylysine 211 (Hyl211) from adjacent polypeptide strands to form a larger collagen trimer.
Molecule of diphenylsulfimide. Molecular model of bars and spheres
Peroxidasin forms hypobromous acid (HOBr) and hypochlorous acid (HOCl) from bromide and chloride, respectively, which may mediate the formation of sulphilimine cross-links.
The bromide, converted into hypobromous acid, forms an intermediate of the bromosulfonium ion (S-Br) that participates in the formation of the cross-links.
McCall, et al. (2014) showed that Br deficiency in the diet is lethal in the Drosophila fly, while the Br replenishment reestablishes its viability.
They also established that bromine is an essential trace element for all animals because of its role in the formation of sulfilimine and collagen IV bonds, which is of vital importance for the formation of basement membranes and tissue development.
References
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- Liu, X., Zheng, A., Luan, D., Wang, X., Kong, F., Tong, L.,... Tang, B. (2017). High-Quantum-Yield Mitochondria-Targeting Near-Infrared Fluorescent Probe for Imaging Native Hypobromous Acid in Living Cells and in Vivo. Analytical Chemistry.
- McCall, A., Cummings, C., Bhave, G., Vanacore, R., Page-McCaw, A., & Hudson, B. (2014). Bromine is an Essential Trace Element for Assembly of Collagen IV Scaffolds in Tissue Development and Architecture. Cell, 157 (6), 1380-1392.
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- PubChem, (2016). Hypobromous acid [image] Recovered from nih.gov.
- Steane, R. (2014). The DNA Molecule - rotatable in 3 dimensions [image] Retrieved from biotopics.co.uk
- Suzuki, T., Kitabatake, A., & Koide, Y. (2016). Reaction of Thymidine with Hypobromous Acid in Phosphate Buffer. Chemical and Pharmaceutical Bulletin, 64 (8), 1235-1238.
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