Viruses as well as other (bio-)colloids possess a pH-dependent surface charge in polar media such as water. This electrostatic charge determines the mobility of the soft particle in an electric field and thus governs its colloidal behaviour which plays a major role in virus sorption processes. The pH value at which the net surface charge switches its sign is referred to as the isoelectric point (abbreviations: pI or IEP) and is a characteristic parameter of the virion in equilibrium with its environmental water chemistry. Here, we review the IEP measurements of viruses that replicate in hosts of kingdom plantae, bacteria and animalia. IEPs of viruses are found in pH range from 1.9 to 8.4; most frequently, they are measured in a band of 3.5 < IEP < 7. However, the data appear to be scattered widely within single virus species. This discrepancy is discussed and should be considered when IEP values are used to account for virus sorption processes.

/pdf/isoelectric-points-of-viruses-4ztrnfp944.pdf

Isoelectric points of viruses

The integration of mass transport control by means of membrane functionality into microfluidic devices has shown substantial growth over the last 10 years. Many different examples of mass transport control have been reported, demonstrating the versatile use of membranes. This review provides an overview of the developments in this area of research. Furthermore, it aims to bridge the fields of microfabrication and membrane science from a membrane point-of-view. First the basic terminology of membrane science will be discussed. Then the integration of membrane characteristics on-chip will be categorized based on the used fabrication method. Subsequently, applications in various fields will be reviewed. Considerations for the use of membranes will be discussed and a checklist with selection criteria will be provided that can serve as a starting point for those researchers interested in applying membrane-technology on-chip. Finally, opportunities for microfluidics based on proven membrane technology will be outlined. A special focus in this review is made on the membrane properties of polydimethylsiloxane (PDMS), since this material is frequently used nowadays in master replication.

Membranes and microfluidics: a review

Over the last three decades, virus-like particles (VLPs) have evolved to become a widely accepted technology, especially in the field of vaccinology. In fact, some VLP-based vaccines are currently used as commercial medical products, and other VLP-based products are at different stages of clinical study. Several remarkable advantages have been achieved in the development of VLPs as gene therapy tools and new nanomaterials. The analysis of published data reveals that at least 110 VLPs have been constructed from viruses belonging to 35 different families. This review therefore discusses the main principles in the cloning of viral structural genes, the relevant host systems and the purification procedures that have been developed. In addition, the methods that are used to characterize the structural integrity, stability, and components, including the encapsidated nucleic acids, of newly synthesized VLPs are analyzed. Moreover, some of the modifications that are required to construct VLP-based carriers of viral origin with defined properties are discussed, and examples are provided.

/pdf/construction-and-characterization-of-virus-like-particles-a-2822ofjxmo.pdf

Construction and Characterization of Virus-Like Particles: A Review

Ultramicro enzyme assays in a capillary electrophoretic system.

A new highly sensitive microscale analytical procedure called affinity probe capillary electrophoresis (APCE) is presented. One of the two species, which can form a biospecific complex, is labeled with a fluorescent dye. The affinity probe is used to detect the analyte as a complex after the separation of the excess free probe by capillary electrophoresis. As an example of this approach, an FAB' fragment of a mouse monoclonal antibody (anti-human growth hormone) was labeled with tetramethylrhodamine-iodoacetamide at a hinge region thiol group. Samples were mixed with the purified labeled antibody fragment, and the associated complex was separated by capillary isoelectric focusing with detection by laser-induced fluorescence. In these preliminary results, methionyl recombinant human growth hormone (met-rhGH) could be successfully determined down to detection levels of approximately 5 x 10(-12) M. Mono- and dideamidated variants of met-rhGH were detected simultaneously with the nondeamidated form of the antigen as separate peaks.

Affinity probe capillary electrophoresis: analysis of recombinant human growth hormone with a fluorescent labeled antibody fragment.

A capillary isoelectric focusing-whole column imaging detection (CIEF-WCID) method was used to determine the isoelectric point (pI) of norovirus virus-like particles (VLPs) The VLPs were produced from noroviruses that represented the two genogroups, genogroup I (Funabashi, Seto, and Norwalk) and genogroup II (Hawaii, Kashiwa, and Narita) Using the imaged CIEF-WCID detection technique, separation was accomplished using a short (4-5 cm) internally coated capillary (100-microm diameter) and a whole-column optical absorption imaging detector operated at 280 nm CIEF-WCID experiments showed the similarity of the pI values of VLPs from genogroups I and II, with pI values of 59, 59, 60, and 60 for Funabashi, Norwalk, Seto, and Hawaii The two other VLPs displayed pI values of 55 (Kashiwa) and 69 (Narita) The VLP peaks were shown to be reproducibility resolved CIEF-WCID shows great promise for norovirus detection in public health, clinical, and food safety applications, as CIEF-WCID overcomes several limitations of the currently used genetic and immunological methods

Isoelectric Point Determination of Norovirus Virus-like Particles by Capillary Isoelectric Focusing with Whole Column Imaging Detection

Universal detection for capillary isoelectric focusing without mobilization using concentration gradient imaging system

The focused patterns of protein samples by capillary isoelectric focusing (CIEF) were monitored without mobilization by a concentration gradient imaging detection system based on the Schileren shadowgraph method. The system consisted of a low-power He-Ne laser and a 1024 pixel charge-coupled device (CCD). The length of the capillary, the position of the CCD sensor, and the separation voltage were optimized. Computer software for background correction and noise reduction was also employed

Capillary isoelectric focusing with a universal concentration gradient imaging system using a charge-coupled photodiode array

A unique imaging detector was constructed for capillary isoelectric focusing (CIEF) by combining a selective optical absorption imaging detector with a universal refractive index gradient imaging detector. All sample zones focused inside a 100-μm-i.d., 4-cm-long capillary by isoelectric focusing were detected in a real-time fashion by the universal imaging detector, and their spectroscopic properties were measured by the absorption imaging detector almost simultaneously. The refractive index gradient imaging is based on a dark-field Toepler-Schlieren system

Dual Detection for Capillary Isoelectric Focusing with Refractive Index Gradient and Absorption Imaging Detectors

Optimizing separation conditions for proteins and peptides using imaged capillary isoelectric focusing

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