Evaluating the zeta potential of proteins at each pH is important in controlling the dispersion/cohesion and adsorption to surfaces of solids such as test containers. Proteins are known to exhibit different isoelectric points depending on the pKa of amino acids forming the proteins.

We used bovine serum albumin (BSA), a protein containing higher ratios of neutral amino acids, and lysozyme, a protein containing higher ratios of basic amino acids, to measure the pH dependence of zeta potential of each.

Protein structure and function are determined by amino acid sequences. Amino acid sequences also determine protein charge states.

We mesured the electrophoretic mobility of acidic proteins using an electrophoretic light scattering photometer to obtain zeta potential. The proteins examined were bovine serum albumin (monometer, Mw = 66,000), ovalbumin (Mw = 45,000), and ß-lactoglobulin B (Mw = 18,000) obtained from Sigma-Aldrich. We prepared samples using a 10 mM phosphate buffer solution (pH 7) at protein concentration of 1 mg/ml and filtrated them through a 0.1 µm filter. Measurements were made at 25oC and zeta potential calculated using the Smoluchowski equation.

In the electrostatic interactions of biomaterials with living tissues, the surface potential on flat materials (cells and skin surfaces) have been rarely evaluated. We prepared human umbilical vein endothelial cells (HUVEC) cultured on polystyrene substrates and examined the effects of different polyion complexes (PIC) adsorbed to their surfaces and electrostatic interactions. PICs were prepared at different mixing ratio of anionic and cationic polymers (cation/anion, C/A ratio). The HUVEC cells were cultured using Endothelial Cell Basal Medium as the culture medium for three days on 1.4 cm x 3.4 cm polystyrene substrte at 37oC, 5% CO2 and 1.2 x 104 cells/cm2, and made confluent. PICs were prepared to achieve C/A ratios of 1.5, 4, and 16 using poly (dimethylaminoethyl methacrylate) (PDMAEMA) as the cationic polymer and plasmid DNA as the anionic polymer. We performed measurements by injection PBS solution in dedicated cells for flat surface potential measurements and setting the samples immersed in the PBS solution.

Used in various industries in containers, packaging electric appliances, automobiles, and pharmaceuticals, plastics are staple of daily life. Compositions range from single materials to composites.

We measured the inner surface potential of various plastic containers: polyethylene (PE), polypropylene (PP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and polyethylene terephthalate (PET).

The term ‘Xylene Solubles’ refers to the percentage of soluble species in homo- and copolymers of polypropylene. Its value correlates to the R21 value and to the amorphous content of the polymer. For polypropylene homopolymers, R21 is a measure of tactility parameters like stiffness and hardness. Investigating copolymers, R21 additionally corresponds to comonomer related parameters such as transparency and gloss. Its measurement is widely used to control the polymerization process and to determine the physical properties of final products for Quality Control.

Historically the xylene soluble content (ISO 16152, ASTM 5492) has been measured by extraction.

With this time consuming method, a direct controlling of the polymerization process is not feasible. In contrast, the TD-NMR application is fast, operator independent and requires no harmful solvents or dedicated lab-space.

Verification of authenticity is a crucial aspect of food quality control, and also important to regulatory organizations. In this study, two wines of known pure varietal along with some commercial wines were examined using a mass spectrometry based chemical sensor. The fast analysis times obtained using this instrument makes this technology ideal for detection of adulteration.

Multivariate statistics were used to create models that discriminate between wine varieties. Exploratory analysis such as principal component analysis (PCA) and hierarchical cluster analysis (HCA) indicated the viability of the data set for classifi cation models. Soft-independent-modeling-of-class-analogy (SIMCA) and K Nearest Neighbors (KNN) were used to create two classification models.

Both SIMCA and KNN provided a quick identification of unknown samples. Overall, the fast identification of wine varieties demonstrates the usefulness of the MS chemical sensor in detecting samples with close chemical composition.

Carpets for office use are nowadays in most cases applied with water-based adhesives. During the last decade the complaints about odors and emission of volatile organic compounds from these fitted carpets have increased dramatically, causing a major problem for indoor air quality. In a series of investigations it has been established that in many cases the adhesives used were the primary cause of complaints. This is initially surprising, since usually sol ventfree water-based dispersion adhesives were used.

This paper describes the analytical approach of analyzing a broad variety of volatile compounds within a wide boiling point range with thermal desorption GC/MS.

Virus-Like Particles (VLPs) are biomolecular nanoparticles formed by controlled self-assembly of viral structural proteins. Lacking viral DNA for replication, VLPs are capable of triggering an immune response without the risk of infection and have been proven to be safe yet highly immunogenic. VLPs are of growing interest in the pharmaceutical and biotechnology industries following the success of blockbuster VLP-based vaccines against hepatitis B and human papillomavirus. These bioparticles are increasingly targeted not only for safe and efficacious immune stimulants but also therapeutic gene delivery agents, taking advantage of their DNA encapsulation and transport capabilities.

With an increasing number of VLPs entering biotherapeutic development pipelines, accelerated development presents several key analytical challenges. Common to all phases of development is the basic biophysical characterization of mass, size, composition and conformation. These and additional, phase-specific properties are required in early stage stability assessment of vaccine candidates; process development; and multiparametric formulation development. In the final product, quality assurance requires identifying and quantifying degradant products such as free capsomeres, partially formed capsids and aggregates.

This paper describes an automated pyrolysis system for gas chromatography (GC) based on a filament type pyrolyzer combined with a commercially available thermal desorption instrument, onto which the pyrolysis module is installed. Automated sample introduction for both pyrolysis and thermal desorption is performed using a commercially available autosampler.

For pyrolysis of solid, liquid, or melting samples the use of different types of sample holders is investigated, for example cup-type holders for liquid samples. A special design has been developed that enables accelerated gas phase transport to help reduce the formation of secondary pyrolysis products. Sample holder design and complete flow path heating are essential design aspects in order to maximize recovery and minimize carry-over, enabling the system to reliably perform automated analysis of batches of different sample types. These aspect are discussed.

The cryo-trap function of the thermal desorption system used enables splitless transfer to the GC/MS of the formed pyrolysis products. An example is presented, in which water containing macromolecule residue in the ppm range is introduced into the pyrolysis module. The water is then removed using a solvent vent step and pyrolysis performed immediately afterwards, enabling quantification of the macromolecules by chromatographic determination of their pyrolysis products.

This paper describes an automated pyrolysis system for gas chromatography (GC) based on a filament type pyrolyzer combined with a commercially available thermal desorption instrument, onto which the pyrolysis module is installed. Automated sample introduction for both pyrolysis and thermal desorption is performed using a commercially available autosampler.

For pyrolysis of solid, liquid, or melting samples the use of different types of sample holders is investigated, for example cup-type holders for liquid samples. A special design has been developed that enables accelerated gas phase transport to help reduce the formation of secondary pyrolysis products. Sample holder design and complete fl ow path heating are essential design aspects in order to maximize recovery and minimize carry-over, enabling the system to reliably perform automated analysis of batches of different sample types. These aspect are discussed.