Degradation of poliovirus by adsorption on inorganic surfaces

Alteration of the specific infectivity of 3H-labeled ribonucleic acid and 14C-protein labeled poliovirus type 1 by adsorption on inorganic surfaces is investigated by application of kinetic theory to data obtained from sequential extractions of adsorbed virus. Some surfaces, e.g., SiO2, appear to have no significant effect. On the other hand, CuO substantially decreases the specific infectivity of adsorbed preparations. Differences in kinetic plots between 3H-labeled ribonucleic acid and 14C-labeled protein suggest that the inactivation observed involves physical disruption of virions. Van der Waals interactions between solid surfaces and virus are suspected to induce spontaneous virion disassembly. Surface catalyzed disassembly in aquatic and soil environments is implicated as an important mechanism controlling enterovirus dissemination. Methods developed here to evaluate complete recovery of adsorbed virus have potenital application to other degradation studied and problems concerning virus recovery from adsorbents used in virus concentrators.     

Degradation of poliovirus by adsorption on inorganic surfaces.

Alteration of the specific infectivity of 3H-labeled ribonucleic acid and 14C-protein labeled poliovirus type 1 by adsorption on inorganic surfaces is investigated by application of kinetic theory to data obtained from sequential extractions of adsorbed virus. Some surfaces, e.g., SiO2, appear to have no significant effect. On the other hand, CuO substantially decreases the specific infectivity of adsorbed preparations. Differences in kinetic plots between 3H-labeled ribonucleic acid and 14C-labeled protein suggest that the inactivation observed involves physical disruption of virions. Van der Waals interactions between solid surfaces and virus are suspected to induce spontaneous virion disassembly. Surface catalyzed disassembly in aquatic and soil environments is implicated as an important mechanism controlling enterovirus dissemination. Methods developed here to evaluate complete recovery of adsorbed virus have potenital application to other degradation studied and problems concerning virus recovery from adsorbents used in virus concentrators.     

Gene conversion in human immunoglobulin gamma locus shown by unusual location of IgG allotypes

The constant region of the gamma 1, gamma 2 and gamma 3 heavy chains of the human IgG1, IgG2 and IgG3 immunoglobulins carries antigenic determinants or G1m, G2m and G3m allotypes, which are genetic markers of these subclasses. The exceptional presence on gamma 1 and gamma 2 chains of Gm allotypes usually located on the CH3 domain of gamma 3 shows an unexpected clustering of base changes and subsequent identity of short DNA sequences in the CH3 exon of the non-allelic gamma 1, gamma 2 and gamma 3 genes. Such clusters of substitutions are not easily explained on the classical basis of point mutations. A gene conversion, which substituted a segment of the gamma 1 or gamma 2 gene with the homologous region of the non-allelic gamma 3 gene, is more likely. Other examples of possible conversion involving the gamma genes are described. The conservation or the restoration of short sequences produced by the conversion events might be related to the biological properties of the constant region of the heavy chains.     

Reduction of albumin adsorption onto silicon surfaces by Tween 20

The ability of Tween 20 to reduce the adsorption of albumin on silicon surfaces of different hydrophobicity was investigated by ellipsometry. As expected, protein adsorption was found to depend on the degree of hydrophobicity of the surfaces and on the concentration of the surfactant. A reduction of 90% in albumin adsorption on hydrophobic methylated surfaces by 0.05% Tween 20 was achieved, whereas a reduction of only 15% on hydrophilic surfaces was observed. Experiments of time-dependent protein adsorption in both pure protein and protein-surfactant mixtures were conducted to ascertain the stability of physically adsorbed Tween 20 films on intermediate silicon surfaces. It was found that the adsorbed Tween 20 film was robust and there was no evidence of exchange of the Tween molecules with albumin for up to 240 min exposure. Adsorption minima were confirmed to correlate with minima in contact angle and critical micelle concentration (CMC). (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 618-625, 1997.     

Estimating the location and shape of hybrid zones

We propose a new model to make use of georeferenced genetic data for inferring the location and shape of a hybrid zone. The model output includes the posterior distribution of a parameter that quantifies the width of the hybrid zone. The model proposed is implemented in the GUI and command-line versions of the Geneland program versions ≥ 3.3.0. Information about the program can be found on http://www2.imm.dtu.dk/gigu/Geneland/.     

Drivers of sett site location by European badgers in Portugal

European badgers (Meles meles) are considered central-place foragers, whose spatial ecology is predominantly determined by sett location. Many studies have assessed the factors determining sett site selection throughout this species’ range, but these have often been geographically limited and have primarily identified locally dependent factors. To infer key factors determining sett location, a broader scale approach is needed. Between June 2014 and January 2017, we surveyed mainland Portugal to detect badger setts in 10?×?10 km cells, corresponding to a total of 657.5 km walked line transects. We detected 54 main setts in 136 surveyed cells. Each sett and non-sett site (i.e. transects without setts) was characterised using bioenvironmental variables (e.g. land cover, presence of human infrastructure, soil). We used generalized linear mixed models to test five hypotheses potentially explaining sett location: land cover composition; anthropogenic disturbance; abiotic environmental drivers; trophic resource availability; and a combined effect of all these factors. Our findings show that the key factors for badger sett site selection in Portugal are: (1) disturbance avoidance (low beehive density; absence of livestock; far from hunting reserves), but with a tendency to be located close to highways and unpaved roads; and (2) ease of excavation (avoidance of sedimentary/metamorphic composite rocks). Although specific factors among these drivers may be more important locally or regionally, these major drivers have also been identified elsewhere in Europe. Our nationwide approach contributes to a broader understanding of general patterns of sett site selection by badgers in southern Europe. Furthermore, it provides the national authorities with novel and broad-scale data to facilitate sustainable species conservation of badgers in the southwestern limit of their range.     

Zein adsorption to hydrophilic and hydrophobic surfaces investigated by surface plasmon resonance

Zein, the prolamine of corn, has been investigated for its potential as an industrial biopolymer. In previous research, zein was plasticized with oleic acid and formed into sheets/films. Physical properties of films were affected by film structure and controlled in turn by zein-oleic acid interactions. The nature of such interactions is not well understood. Thus, protein-fatty acid interactions were investigated in this work by the use of surface plasmon resonance (SPR). Zein adsorption from 75% aqueous 2-propanol solutions, 0.05% to 0.5% w/v, onto hydrophilic and hydrophobic self-assembled monolayers (SAMs) formed by 11-mercaptoundecanoic acid and 1-octanethiol, respectively, was monitored by high time resolution SPR. Initial adsorption rate and ultimate surface coverage increased with bulk protein concentration for both surfaces. The initial slope of plotted adsorption isotherms was higher on 11-mercaptoundecanoic acid than on 1-octanethiol, indicating higher zein affinity for hydrophilic SAMs. Also, maximum adsorption values were higher for zein on hydrophilic than on hydrophobic SAMs. Flushing off loosely bound zein in the SPR cell allowed estimation of apparent monolayer values. Differences in monolayer values for hydrophobic and hydrophilic surfaces were explained in terms of zein adsorption footprint.     

Virus adsorption to mineral surfaces is reduced by microbial overgrowth and organic coatings

In experiments with strains of poliovirus, reovirus, echovirus, and Coxsackievirus, overgrowth with exopolymer-forming bacteria reduced virus adsorption to mineral surfaces. Adsorption was improved when organic materials adsorbed to minerals were removed by low-temperature ashing. In a soil series, virus adsorption increased with soil depth. This paralleled a decrease in organic content, but differences in charge development of the soil particles may also be involved. Prolonged (40-year) irrigation with treated sewage effluents, leading to a buildup of organic coatings, also decreased adsorption. However, saturation of the virus-binding capacity of the soil as a result of continuous exposure to virus-containing effluents was not apparent.     

Competitive protein adsorption on polysaccharide and hyaluronate modified surfaces

Adsorption of bovine serum albumin (BSA) and fibrinogen (Fg) was measured on six distinct bare and dextran- and hyaluronate-modified silicon surfaces created using two dextran grafting densities and three hyaluronic acid (HA) sodium salts derived from human umbilical cord, rooster comb and Streptococcus zooepidemicus. Film thickness and surface morphology depended on the HA molecular weight and concentration. BSA coverage was enhanced on surfaces in competitive adsorption of BSA:Fg mixtures. Dextranization differentially reduced protein adsorption onto surfaces based on oxidation state. Hyaluronization was demonstrated to provide the greatest resistance to protein coverage, equivalent to that of the most resistant dextranized surface. Resistance to protein adsorption was independent of the type of HA utilized. With changing bulk protein concentration from 20 to 40 μg ml(-1) for each species, Fg coverage on silicon increased by 4x, whereas both BSA and Fg adsorption on dextran and HA were far less dependent on protein bulk concentration.     

Friction between cellulose surfaces and effect of xyloglucan adsorption

The forces and friction between cellulose spheres have been measured in the absence and presence of xyloglucan using an atomic force microscope. The forces between cellulose are monotonically repulsive with negligible adhesion after contact is achieved. The friction coefficient is observed to be unusually high in comparison with other nanotribological systems. We have confirmed that xyloglucan adsorbs strongly to cellulose, which results in a much stronger adhesion, which is dependent on the time the surfaces are in contact. Xyloglucan also increases the repulsion on approach of the cellulose surfaces, and the friction is markedly reduced. The apparently incompatible observations of decreased friction in combination with increased adhesion fulfills many of the necessary criteria for a papermaking additive.     

Competitive protein adsorption on polysaccharide and hyaluronate modified surfaces

Adsorption of bovine serum albumin (BSA) and fibrinogen (Fg) was measured on six distinct bare and dextran- and hyaluronate-modified silicon surfaces created using two dextran grafting densities and three hyaluronic acid (HA) sodium salts derived from human umbilical cord, rooster comb and Streptococcus zooepidemicus. Film thickness and surface morphology depended on the HA molecular weight and concentration. BSA coverage was enhanced on surfaces in competitive adsorption of BSA:Fg mixtures. Dextranization differentially reduced protein adsorption onto surfaces based on oxidation state. Hyaluronization was demonstrated to provide the greatest resistance to protein coverage, equivalent to that of the most resistant dextranized surface. Resistance to protein adsorption was independent of the type of HA utilized. With changing bulk protein concentration from 20 to 40 μg ml^?1 for each species, Fg coverage on silicon increased by 4x, whereas both BSA and Fg adsorption on dextran and HA were far less dependent on protein bulk concentration.     

Molecular modeling of B-DNA site recognition by Ru intercalators: molecular shape selection

In this work, molecular modeling methods have been applied to the interaction characterization of polypyridyl transitional-metal complexes with the oligonucleotide (B-DNA fragment). In order to explore the factors governing the groove recognition and intercalative depth, we establish a simple and practical docking method (step-by-step docking operation) to obtain potential curves while making complexes inset into B-DNA along an assigned path. Energy values in the potential curve are obtained from energy minimization of binding geometries. Modeling results clearly show that the optimum binding conformation corresponding to the global minimum in the potential curve for each complex is found to correlate well with the experimental results. Our results also confirm that minor changes of the ligand structure can lead to profound influences on binding geometries, so the molecular shape of the complexes is a predominant factor in governing the binding mode. Moreover, we find that the vdW force and water molecular effect are strongly associated with molecular-shape selection in our model. These results complement and extend the knowledge of the nature of these complexes binding to B-DNA.Figure Schematic illustration of metal complexes bound to B-DNA. The complexes are intercalated into the A₅T₆/T₆A₅ base step via a head-on fashion     

Ligand binding: functional site location,similarity and docking

Computational methods for the detection and characterisation of protein ligand-binding sites have increasingly become an area of interest now that large amounts of protein structural information are becoming available prior to any knowledge of protein function. There have been particularly interesting recent developments in the following areas: first, functional site detection, whereby protein evolutionary information has been used to locate binding sites on the protein surface; second, functional site similarity, whereby structural similarity and three-dimensional templates can be used to compare and classify and potentially locate new binding sites; and third, ligand docking, which is being used to find and validate functional sites, in addition to having more conventional uses in small-molecule lead discovery.     

Characterization of eukaryotic cell surfaces prior to and after serum protein adsorption by X-ray photoelectron spectroscopy

Elemental surface concentration ratios N/C, O/C, and P/C of fibroblasts, HELA epithelial cells, and smooth muscle cells, prior to and after washing in the absence or presence of serum proteins, were determined by X-ray photoelectron spectroscopy. Cell surfaces appeared to adsorb hardly any serum proteins, and the relatively high P/C, as compared to N/C and O/C, elemental surface concentration ratio indicated that the cell surfaces consisted mainly of the phospholipid bilayer, with little or no proteins present. The lack of adsorption of serum proteins to the cell surfaces seems at odds with the common notion that cells require adhesive proteins in order to adhere and spread. However, the adsorption behavior of cellularly produced proteins may be completely different, particularly since they seem to be able to displace adsorbed serum proteins from biomaterials surfaces. Interestingly, only HELA epithelial cells (a tumor cell line) appeared to adsorb a very small amount of proteins.     

Reduction of irreversible protein adsorption on solid surfaces by protein engineering for increased stability

The influence of protein stability on the adsorption and desorption behavior to surfaces with fundamentally different properties (negatively charged, positively charged, hydrophilic, and hydrophobic) was examined by surface plasmon resonance measurements. Three engineered variants of human carbonic anhydrase II were used that have unchanged surface properties but large differences in stability. The orientation and conformational state of the adsorbed protein could be elucidated by taking all of the following properties of the protein variants into account: stability, unfolding, adsorption, and desorption behavior. Regardless of the nature of the surface, there were correlation between (i) the protein stability and kinetics of adsorption, with an increased amplitude of the first kinetic phase of adsorption with increasing stability; (ii) the protein stability and the extent of maximally adsorbed protein to the actual surface, with an increased amount of adsorbed protein with increasing stability; (iii) the protein stability and the amount of protein desorbed upon washing with buffer, with an increased elutability of the adsorbed protein with increased stability. All of the above correlations could be explained by the rate of denaturation and the conformational state of the adsorbed protein. In conclusion, protein engineering for increased stability can be used as a strategy to decrease irreversible adsorption on surfaces at a liquid-solid interface.     

The investigation of Protein A and Salmonella antibody adsorption onto biosensor surfaces by atomic force microscopy

The investigation of Protein A and antibody adsorption on surfaces in a biological environment is an important and fundamental step for increasing biosensor sensitivity and specificity. The atomic force microscope (AFM) is a powerful tool that is frequently used to characterize surfaces coated with a variety of molecules. We used AFM in conjunction with scanning electron microscopy to characterize the attachment of protein A and its subsequent binding to the antibody and Salmonella bacteria using a gold quartz crystal. The rms roughness of the base gold surface was determined to be approximately 1.30 nm. The average step height change between the solid gold and protein A layer was approximately 3.0 +/- 1.0 nm, while the average step height of the protein A with attached antibody was approximately 6.0 +/- 1.0 nm. We found that the antibodies did not completely cover the protein A layer, instead the attachment follows an island model. Salt crystals and water trapped under the protein A layer were also observed. The uneven adsorption of antibodies onto the biosensor surface might have led to a decrease in the sensitivity of the biosensor. The presence of salt crystals and water under the protein A layer may deteriorate the sensor specificity. In this report, we have discussed the application and characterization of protein A bound to antibodies which can be used to detect bacterial and viral pathogens.