Gabriel Cavalli

Covalent Attachment of Proteins to Solid Supports and Surfaces via Sortase-Mediated Ligation

Background There is growing interest in the attachment of proteins to solid supports for the development of supported catalysts, affinity matrices, and micro devices as well as for the development of planar and bead based protein arrays for multiplexed assays of protein concentration, interactions, and activity. A critical requirement for these applications is the generation of a stable linkage between the solid support and the immobilized, but still functional, protein. Methodology Solid supports including crosslinked polymer beads, beaded agarose, and planar glass surfaces, were modified to present an oligoglycine motif to solution. A range of proteins were ligated to the various surfaces using the Sortase A enzyme of S. aureus. Reactions were carried out in aqueous buffer conditions at room temperature for times between one and twelve hours. Conclusions The Sortase A transpeptidase of S. aureus provides a general, robust, and gentle approach to the selective covalent immobilization of proteins on three very different solid supports. The proteins remain functional and accessible to solution. Sortase mediated ligation is therefore a straightforward methodology for the preparation of solid supported enzymes and bead based assays, as well as the modification of planar surfaces for microanalytical devices and protein arrays.

New approach to produce water free of bacteria, viruses, and halogens in a recyclable system.

ABSTRACT The antimicrobial activity of a new cross-linked N-halamine polymer against bacteria and viruses was evaluated. The polymer achieved a 9-log10 reduction of bacteria (both Escherichia coli and Staphylococcus aureus) in 1.5 h and a 5-log10 reduction of bacteriophage PRD1 in 3 h. At the same time, the ability of the nonhalogenated polymer to trap halide ions was examined. The polymer was incorporated into a multifiltration system to study the ability to produce water free of bacteria, viruses, and halide ions. The antimicrobial activity, useful lifetime, halide ion level, and recycling possibilities of the system were quantified on a laboratory scale. A design for a large-scale multifiltration system based on this polymer is proposed.

Removal of organic micropollutants using membrane-assisted processes: a review of recent progress

The health risk of organic micro pollutants in water is yet to be comprehensively established. However, the persistence of these pollutants in the environment as a result of continuous discharge even at trace concentrations is considered to pose major environmental concerns. Advance treatment methods such as membrane-assisted processes (MAPs) are potential technologies capable of removing a wide range of these organic micropollutants (OMPs) detected in water. Tight membranes as regards pore size are reported to be more efficient than loose membranes mainly because of the removal mechanism involved, which is mainly influenced by the properties of the membrane and the pollutants in relation to solute–solute and solute–membrane interaction. The study and application of membrane processes to water and wastewater treatment have grown significantly in the last decade. Membrane processes application is diverse and flexible enough to allow adaptation into other physicochemical processes. Integration and hybridization of membrane processes with other physicochemical processes and natural systems are becoming a more economical and sustainable option for removal of OMPs. Nevertheless, there are shortfalls in the industrial application of membrane-assisted technologies. This paper reviews and assesses the applicability of various MAPs applied for the removal of OMPs from water and wastewater streams.

Straw N-halamines: evaluation in single and multistage filtration systems.

New N-halamines (I-Cl and II-Cl) based on cellulose extracted from rice straw have been evaluated in single and multistage filtration systems against bacteria and viruses. Escherichia coli and Staphylococcus aureus were used as examples of Gram-negative and Gram-positive bacteria respectively while PRD1 bacteriophage was used as an example for viruses. II-Cl has achieved 9 log reductions in viable counts against E. coli in 2 h and S. aureus in 1h while it has achieved 7 log reductions against PRD1 in 5 h. The particle size of prepared materials was modified as well as the flow rate through the filtration systems. The antimicrobial activity of modified cellulose was proved to be comparable to some synthetic biocidal polymers from the same type in similar water treatment systems.

Quantifying the Effect of Polymer Blending through Molecular Modelling of Cyanurate Polymers

Modification of polymer properties by blending is a common practice in the polymer industry. We report here a study of blends of cyanurate polymers by molecular modelling that shows that the final experimentally determined properties can be predicted from first principles modelling to a good degree of accuracy. There is always a compromise between simulation length, accuracy and speed of prediction. A comparison of simulation times shows that 125ps of molecular dynamics simulation at each temperature provides the optimum compromise for models of this size with current technology. This study opens up the possibility of computer aided design of polymer blends with desired physical and mechanical properties.

What are we going to do about a problem like polymer chemistry? Develop new methods of delivery to improve understanding of a demanding interdisciplinary topic

Following collaboration between two chemistry lecturers and an academic developer an attempt was made to enhance the learning of students within a chemistry module through the adaptation of the delivery of content material. This paper reports a piece of practitioner led research which considered how effective the approach developed was upon the level of student understanding and the process through which this occurred. The module delivery was altered from an emphasis on the transmission of knowledge through a traditional lecture format, to rotating small group problem based sessions and the use of concept maps. Student feedback and higher grades achieved appear to demonstrate it was effective.

Horizontal Patterns of Single Wall Carbon Nanotubes by Simple Filtration Method

This work demonstrates the horizontal patterning/alignment of single wall nano tubes (SWNTs) using simple filtration method. In the quest of vertical alignment of SWNTs to fabricate the vertically aligned CNT-membrane, this horizontal patterns as observed by simple filtration technique has been achieved. These horizontal patterns are key arrangements sought in the electronic field and fabrication of CNT-nano composites of required characteristics. In this work SWNTs purified/oxidized treatment with nitric acid at 120-122°C. Oxidized SWNTs further reacted with Octadecyl amine at same temperature to make them significantly dispersible/soluble in solvents especially in Tetrahydrofuran (THF). These modified SWNTs dissolved in THF by sonication and uniform black color solution was obtained that did not settle upon prolonged time of standing. This solution is subsequently filtered through 0.2 micro porous PTFE filter using long neck sintered funnel for horizontal alignment. The inter tube gap between CNTs is initially filled by the precursor reactive vapor stream that is consolidated as a solid polymer through insitu polymerization. Transform Infrared (FTIR) analysis was performed to find the attached functional groups. Alignment of functionalized SWNTs collected on PTFE filter was analyzed by Field-emission scanning electron microscopy (FE-SEM). Ordered horizontal patterns were observed. The contemporary horizontal alignment techniques being used are tedious and need very special facilities. The current method is comparatively quite simple and large quantities of CNTs can be aligned to advantage.