The Impact of Capsid Proteins on Virus Removal and Inactivation during Water Treatment Processes

Abstract

This study examined the effect of the amino acid composition of protein capsids on virus inactivation using ultraviolet (UV) irradiation and titanium dioxide photocatalysis, and physical removal via enhanced coagulation using ferric chloride. Although genomic damage is likely more extensive than protein damage for viruses treated using UV, proteins are still substantially degraded. All amino acids demonstrated significant correlations with UV susceptibility. The hydroxyl radicals produced during photocatalysis are considered nonspecific, but they likely cause greater overall damage to virus capsid proteins relative to the genome. Oxidizing chemicals, including hydroxyl radicals, preferentially degrade amino acids over nucleotides, and the amino acid tyrosine appears to strongly influence virus inactivation. Capsid composition did not correlate strongly to virus removal during physicochemical treatment, nor did virus size. Isoelectric point may play a role in virus removal, but additional factors are likely to contribute.

Viruses in wastewater: occurrence, abundance and detection methods

“…The outer surface of non-enveloped viruses is composed of capsid proteins whose isoelectric point is typically below the pH of wastewater. Therefore, this class of viruses has a net surface negative electrical charge ( Hamza et al, 2009 ; Mayer et al, 2015 ). The use of electronegative membranes, common in VIRADEL methods, requires the lowering of the pH prior to filtration in order to induce the protonation of the protein capsid and the resultant inversion of the electrical charge of the viral surface ( Hamza et al, 2009 ).…”

Biophysical Aspects of Interactions at the Bionanointerface between Viruses and Metal and Metal Oxide Nanomaterials

“…The amino acids adjacent to nucleotides get degraded; tyrosine plays a signifi cant role during the activation of the virus. During physicochemical treatment does not aff ect the capsid composition and the size of the virus [38].…”

Bacteriophage inactivation as a function of ferrous iron oxidation

“…We are not aware of any previous disinfection study comparing these two bacteriophages, so it is unclear if P22 is more susceptible to all oxidants than MS2, or if P22 is particularly susceptible to ferrous iron. P22 (52 -60 nm diameter) is a larger phage than MS2 (24 -27 nm diameter), 40,41 and may therefore have a larger exposed surface area during combined coagulation/disinfection. As a tailed bacteriophage, P22's physical structure for attachment and penetration to host bacteria is also exposed to the environment.…”

“…Therefore, close proximity between ferrous iron and the virus may be necessary to ensure that virus inactivation can compete with ferrous autoxidation. Both MS2 and P22 are negatively charged near neutral pH, 10,57 and would therefore attract positively-charged ferrous species. A slower rate of oxidation would allow more time for contact between virions and ferrous ions prior to inclusion of both species in flocs.…”