Effects of chaotropic and antichaotropic agents on elution of poliovirus adsorbed on membrane filters.

Abstract

The association of poliovirus with membrane filters results from both electrostatic and hydrophobic interactions. At low pH, electrostatic interactions appear to dominate. However, at high pH, hydrophobic interactions appear to dominate with both Mfllipore and Zeta plus filters. With both filters, viral elution was prevented at high pH by the presence ofantichaotropic salts, which strengthen hydrophobic associations. This effect was antagonized by detergents and by chaotropic salts, which weaken hydrophobic associations. Excellent correlation was observed between viral elution, the solubilization of adenine, and the micelleformation process in the presence ofchaotropic and antichaotropic agents. Such simple measurements of the relative ability of solvents to accomodate hydrophobic groups may be of predictive value in designing methods for concentration and purification of viruses. The hythesis that hydrophobic interactions are the primary force involved in the stabilization ofvirus attachment at high pH is consistent with observations that cannot be explained by consideration of electrostatic interactions as the major stabilizing factor. difficult to explain solely on the basis ofsuch electrostatic interactions. For example, solutions of beefextract or casein at pH 9 are capable ofeluting viruses associated with Millipore and Zeta plus membrane filters. However, solutions of hydrolyzed protein (casamino acids) or of an individual amino acid (aspartic acid) at the same concentration and pH do not elute viruses from these filters (7). Further, the nonionic compound urea (7) and the detergents sodium lauryl sulfate and Tween 80 (1, 8) promote elution ofvirus.In an attempt to explain the variable effects of different solutions on the elution ofviruses from membrane filters, we have explored hydrophobic interactions as an alternative to the hypothesis of electrostatic interactions for viral retention at high pH. In these studies, we examined the effects ofchaotropic and antichaotropic salts (9) on the elution of viruses adsorbed to membrane filters.

Influence of Salts on Virus Adsorption to Microporous Filters

“…From the results of this and other studies (6,12,20,21) we concluded that certain salt cations promote hydrophobic interactions between a virus and a filter or substrate. The cations that are most effective are smaller, monovalent or multivalent ions (6,12).…”

“…In fact, chelators have been found to promote, rather than interfere with, virus adsorption to microporous filters (6). The study of Farrah (6) and other studies showed that increased virus adsorption to certain microporous filters in the presence of cations and anions was influenced by hydrophobic interactions (6,12,21). Therefore, the adsorption of MS2 and poliovirus 1 in the presence of salts to filters was best explained by the presence of hydrophobic interactions between the filters and the viruses.…”

“…The cations that are most effective are smaller, monovalent or multivalent ions (6,12). These salt cations also interfere with the electrostatic interactions that might occur between a virus and a filter.…”

“…The Filterite filters have a net negative charge at pH values near neutrality, in contrast to the 1MDS filters, which are positively charged or have a slight negative charge at similar pH values (14,24). Nitrocellulose filters (Millipore HA filters) also have a net negative charge at pH 7 (14) and have been used in studies on virus adsorption and to recover viruses from water (6,7,12,28). Cellulose filters (Whatman filters) were included as an example of filters that poorly adsorb viruses.…”

Virus-Binding Proteins Recovered from Bacterial Culture Derived from Activated Sludge by Affinity Chromatography Assay Using a Viral Capsid Peptide

“…This characteristic of urea was thought to contribute to the efficient extraction of crude protein and isolation of VBPs from bacterial cultures derived from activated sludge. The mechanism of adsorbing VBPs to the viral peptide in the affinity column cannot be explained by the simple electrostatic attraction and hydrophobic effect, although they have been reported as main factors in the adsorption of viruses to several substances, such as clay, sandy soil, estuarine sediments, and so on (5,6,21,22,26,39). Under the condition of the start buffer (pH 8.0), the net charge of the viral peptide in the affinity column was expected to be negative, because the pI of the immobilized viral peptide was estimated to be 3.88 (34).…”