Coagulation of tobacco mosaic virus in alcohol–water–LiCl solutions

Alcohol-perturbed self-assembly of the tobacco mosaic virus coat protein

The self-assembly of the tobacco mosaic virus coat protein is significantly altered in alcohol-water mixtures. Alcohol cosolvents stabilize the disk aggregate and prevent the formation of helical rods at low pH. A high alcohol content favours stacked disk assemblies and large rafts, while a low alcohol concentration favours individual disks and short stacks. These effects appear to be caused by the hydrophobicity of the alcohol additive, with isopropyl alcohol having the strongest effect and methanol the weakest. We discuss several effects that may contribute to preventing the protein-protein interactions between disks that are necessary to form helical rods.

Template-Directed Synthesis of Porous and Protective Core-Shell Bionanoparticles

Metal-organic frameworks (MOFs) are promising high surface area coordination polymers with tunable pore structures and functionality; however, a lack of good size and morphological control over the as-prepared MOFs has persisted as an issue in their application. Herein, we show how a robust protein template, tobacco mosaic virus (TMV), can be used to regulate the size and shape of as-fabricated MOF materials. We were able to obtain discrete rod-shaped TMV@MOF core-shell hybrids with good uniformity, and their diameters could be tuned by adjusting the synthetic conditions, which can also significantly impact the stability of the core-shell composite. More interestingly, the virus particle underneath the MOF shell can be chemically modified using a standard bioconjugation reaction, showing mass transportation within the MOF shell.

Enhancing Antibody Response against Small Molecular Hapten with Tobacco Mosaic Virus as a Polyvalent Carrier

Virus nanoparticles (VNPs) have been applied as carrier proteins for effective vaccine development. In this paper, we report the usage of tobacco mosaic virus (TMV) as a carrier for the display of the small molecule estriol (E3), a weakly immunogenic hapten. A highly efficient copper (I)-catalyzed azide-alkyne cycloaddition reaction (CuAAC) was performed for the conjugation of E3 onto TMV capsid at tyrosine (Tyr) 139, by which the antigen density could be controlled. The immune properties of these constructs were evaluated in mice. We found that a strong and long-term antibody response was elicited by conjugating a high density of small molecular haptens on TMV through an oligo(ethylene glycol) (OEG) linker, likely due to the effective activation of B-cells. This study suggests that TMV can serve as a promising platform to induce strong humoral immune responses and that the optimized conjugation strategy was critical to produce high quality antibodies.

Sweep flocculation and adsorption of viruses on aluminum flocs during electrochemical treatment prior to surface water microfiltration

Bench-scale experiments were performed to evaluate virus control by an integrated electrochemical-microfiltration (MF) process from turbid (15 NTU) surface water containing moderate amounts of dissolved organic carbon (DOC, 5 mg C/L) and calcium hardness (50 mg/L as CaCO3). Higher reductions in MS2 bacteriophage concentrations were obtained by aluminum electrocoagulation and electroflotation compared with conventional aluminum sulfate coagulation. This was attributed to electrophoretic migration of viruses, which increased their concentrations in the microenvironment of the sacrificial anode where coagulant precursors are dissolved leading to better destabilization during electrolysis. In all cases, viruses were not inactivated implying measured reductions were solely due to their removal. Sweep flocculation was the primary virus destabilization mechanism. Direct evidence for virus enmeshment in flocs was provided by two independent methods: quantitative elution using beef extract at elevated pH and quantitating fluorescence from labeled viruses. Atomic force microscopy studies revealed a monotonically increasing adhesion force between viruses immobilized on AFM tips and floc surfaces with electrocoagulant dosage, which suggests secondary contributions to virus uptake on flocs from adsorption. Virus sorption mechanisms include charge neutralization and hydrophobic interactions with natural organic matter removed during coagulation. This also provided the basis for interpreting additional removal of viruses by the thick cake formed on the surface of the microfilter following electrocoagulation. Enhancements in virus removal as progressively more aluminum was electrolyzed therefore embodies contributions from (i) better encapsulation onto greater amounts of fresh Al(OH)3 precipitates, (ii) increased adsorption capacity associated with higher available coagulant surface area, (iii) greater virus-floc binding affinity due to effective charge neutralization and hydrophobic interactions, and/or (iv) additional removal by a dynamic membrane if a thick cake layer of flocs is deposited.

Transition force measurement between two negligibly charged surfaces: a new perspective on nanoparticle halos

Since 2001, silica microspheres have been reported to be stabilized by highly charged hydrous ZrO(2) nanoparticles which form halos around the microspheres at pH 1.5. However, the exact mechanisms behind this novel stabilization method in terms of the relevant interaction forces remain unclear. In order to gain a greater insight into this mechanism, the interaction between a silica flat and a silica sphere in different ZrO(2) nanoparticle suspensions was investigated by the colloid probe technique. The interaction force between a silica flat and a 600 nm silica sphere was first investigated in a ZrO(2) nanoparticle (D approximately 8 nm) suspension with volume fractions of 10(-3), 10(-4), 10(-5), and 10(-6). When the volume fraction of ZrO(2) is 10(-6), only a purely attractive van der Waals force was observed between the silica surfaces. With an increase in the ZrO(2) nanoparticle volume fraction, a peak was detected on the transition force curve at a ZrO(2) volume fraction of 10(-5) while a purely repulsion force was observed for ZrO(2) volume fractions of 10(-4) and 10(-3). The average distance difference between the peak and the zero distance point on the transition force curve which should define the distance between the halo on the microsphere is approximately 2.3 nm. Additionally, the repulsion increases with the effective zeta potential of the binary composite sphere (BCS, the entity of the silica sphere and the surrounding zirconia particles) on an increase of the nanoparticle volume fraction while the adhesion force decreases, which indicates a denser nanoparticle halo.