A capillary electrophoresis technique for evaluating botulinum neurotoxin B light chain activity

In vitro potency determination of botulinum neurotoxin B based on its receptor-binding and proteolytic characteristics

Botulinum neurotoxins (BoNTs) are the most potent toxins known. However, the paralytic effect caused by BoNT serotypes A and B is taken advantage of to treat different forms of dystonia and in cosmetic procedures. Due to the increasing areas of application, the demand for BoNTs A and B is rising steadily. Because of the high toxicity, it is mandatory to precisely determine the potency of every produced BoNT batch, which is usually accomplished by performing toxicity testing (LD50 test) in mice. Here we describe an alternative in vitro assay for the potency determination of the BoNT serotype B. In this assay, the toxin is first bound to its specific receptor molecules. After the proteolytic subunit of the toxin has been released and activated by chemical reduction, it is exposed to synaptobrevin, its substrate protein. Finally the proteolytic cleavage is quantified by an antibody-mediated detection of the neoepitope, reaching a detection limit below 0.1mouseLD50/ml. Thus, the assay, named BoNT/B binding and cleavage assay (BoNT/B BINACLE), takes into account the binding as well as the protease function of the toxin, thereby measuring its biological activity.

A two-stage multiplex method for quantitative analysis of botulinum neurotoxins type A, B, E, and F by MALDI-TOF mass spectrometry

In this publication, we report on the development of a quantitative enzymatic method for the detection of four botulinum neurotoxin (BoNT) serotypes responsible for human botulism by MALDI-TOF mass spectrometry. Factors that might affect the linearity and dynamic range for detection of BoNT cleavage products were initially examined, including the amount of peptide substrate and internal standard, the timing of cleavage reaction, and the components in the reaction solution. It was found that a long incubation time produced sensitive results, but was not capable of determining higher toxin concentrations, whereas a short incubation time was less sensitive so that lower toxin concentrations were not detected. In order to overcome these limitations, a two-stage analysis strategy was applied. The first stage analysis involved a short incubation period (e.g., 30 min). If no toxin was detected at this stage, the cleavage reaction was allowed to continue and the samples were analyzed at a second time point (4 h), so that toxin levels lower than 1 mouse LD50 or 55 attomoles per milliliter (55 amol/mL) could be quantified. By combining the results from two-stage quantification, 4 or 5 orders of magnitude in dynamic range were achieved for the detection of the serotypes of BoNT/A, BoNT/B, BoNT/E, or BoNT/F. The effect of multiplexing the assay by mixing substrates for different BoNT serotypes into a single reaction was also investigated in order to reduce the numbers of the cleavage reactions and save valuable clinical samples.

Synthetic substrate for application in both high and low throughput assays for botulinum neurotoxin B protease inhibitors

A FRET peptide substrate was synthesized and evaluated for enzymatic cleavage by the BoNT/B light chain protease. The FRET substrate was found to be useful in both a high throughput assay to uncover initial 'hits' and a low throughput HPLC assay to determine kinetic parameters and modes of inhibition.

A capillary electrophoresis method to assay catalytic activity of botulinum neurotoxin serotypes: Implications for substrate specificity

The potent botulinum neurotoxin inhibits neurotransmitter release at cholinergic nerve terminals, causing a descending flaccid paralysis characteristic of the disease botulism. The currently expanding medical use of the neurotoxin to treat several disorders, as well as the potential misuse of the neurotoxin as an agent in biowarfare, has made understanding of the nature of the toxin's catalytic activity and development of inhibitors critical. To study the catalytic activity of botulinum neurotoxin more thoroughly and characterize potential inhibitors, we have developed a capillary electrophoresis method to measure catalytic activity of different serotypes of botulinum neurotoxin using peptides derived from the native substrates. This assay requires only a minute amount of sample (25 nl), is relatively rapid (15 min/sample), and allows the determination of enzyme kinetic constants for a more sophisticated characterization of inhibitors and neurotoxin catalytic activity. Using this method, we can measure activity of five of the seven serotypes of botulinum neurotoxin (A, B, E, F, and G) with two peptide substrates. Botulinum neurotoxin serotypes C and D did not cleave our peptides, lending insight into potential substrate requirements among the serotypes.

Capillary electrophoresis of proteins 2003-2005

This review article with 304 references describes recent developments in CE of proteins, and covers the two years since the previous review (Hutterer, K., Dolník, V., Electrophoresis 2003, 24, 3998-4012) through Spring 2005. It covers topics related to CE of proteins, including modeling of the electrophoretic migration of proteins, sample pretreatment, wall coatings, improving separation, various forms of detection, special electrophoretic techniques such as affinity CE, CIEF, and applications of CE to the analysis of proteins in real-world samples including human body fluids, food and agricultural samples, protein pharmaceuticals, and recombinant protein preparations.

Probing affinity via capillary electrophoresis: advances in 2003–2004

This review addresses recent advances in capillary electrophoresis of biological-based molecular interaction from a broader perspective, based on applications reported during the period 2003-2004. These capillary electrophoresis-based studies of molecular interactions include affinity capillary electrophoresis, electrokinetic chromatography, and free zone electrophoresis. The review is written as a general synopsis of applications and does not cover the theory or protocol involved in the implementation of the analyses.