Direct and simple detection of recombinant proteins from cell lysates using differential scanning fluorimetry

Application of temperature-responsive HIS-tag fluorophores to differential scanning fluorimetry screening of small molecule libraries

Differential scanning fluorimetry is a rapid and economical biophysical technique used to monitor perturbations to protein structure during a thermal gradient, most often by detecting protein unfolding events through an environment-sensitive fluorophore. By employing an NTA-complexed fluorophore that is sensitive to nearby structural changes in histidine-tagged protein, a robust and sensitive differential scanning fluorimetry (DSF) assay is established with the specificity of an affinity tag-based system. We developed, optimized, and miniaturized this HIS-tag DSF assay (HIS-DSF) into a 1536-well high-throughput biophysical platform using the Borrelial high temperature requirement A protease (BbHtrA) as a proof of concept for the workflow. A production run of the BbHtrA HIS-DSF assay showed a tight negative control group distribution of T_m values with an average coefficient of variation of 0.51% and median coefficient of variation of compound T_m of 0.26%. The HIS-DSF platform will provide an additional assay platform for future drug discovery campaigns with applications in buffer screening and optimization, target engagement screening, and other biophysical assay efforts.

Heterologous expression of Deinococcus geothermalis amylosucrase in Corynebacterium glutamicum for luteolin glucoside production

Amylosucrase (ASase) has great industrial potential owing to its multifunctional activities, including transglucosylation, polymerization, and isomerization. In the present study, the properties of Deinococcus geothermalis ASase (DGAS) expressed in Corynebacterium glutamicum (cDGAS) and purified via Ni-NTA affinity chromatography were compared to those of DGAS expressed in Escherichia coli (eDGAS). The pH profile of cDGAS was similar to that of eDGAS, whereas the temperature profile of cDGAS was lower than that of eDGAS. The melting temperature of both enzymes did not differ significantly. Interestingly, polymerization activity was slightly lower in cDGAS than in eDGAS, whereas luteolin (an acceptor molecule) transglucosylation activity in cDGAS was 10 % higher than that in eDGAS. Analysis of protein secondary structure via circular dichroism spectroscopy revealed that cDGAS had a lower strand/helix ratio than eDGAS. The present results indicate that cDGAS is of greater industrial significance than eDGAS.

AAV-ID: A Rapid and Robust Assay for Batch-to-Batch Consistency Evaluation of AAV Preparations

Adeno-associated virus (AAV) vectors are promising clinical candidates for therapeutic gene transfer, and a number of AAV-based drugs may emerge on the market over the coming years. To insure the consistency in efficacy and safety of any drug vial that reaches the patient, regulatory agencies require extensive characterization of the final product. Identity is a key characteristic of a therapeutic product, as it ensures its proper labeling and batch-to-batch consistency. Currently, there is no facile, fast, and robust characterization assay enabling to probe the identity of AAV products at the protein level. Here, we investigated whether the thermostability of AAV particles could inform us on the composition of vector preparations. AAV-ID, an assay based on differential scanning fluorimetry (DSF), was evaluated in two AAV research laboratories for specificity, sensitivity, and reproducibility, for six different serotypes (AAV1, 2, 5, 6.2, 8, and 9), using 67 randomly selected AAV preparations. In addition to enabling discrimination of AAV serotypes based on their melting temperatures, the obtained fluorescent fingerprints also provided information on sample homogeneity, particle concentration, and buffer composition. Our data support the use of AAV-ID as a reproducible, fast, and low-cost method to ensure batch-to-batch consistency in manufacturing facilities and academic laboratories.

Meltdown: A Tool to Help in the Interpretation of Thermal Melt Curves Acquired by Differential Scanning Fluorimetry

The output of a differential scanning fluorimetry (DSF) assay is a series of melt curves, which need to be interpreted to get value from the assay. An application that translates raw thermal melt curve data into more easily assimilated knowledge is described. This program, called "Meltdown," conducts four main activities--control checks, curve normalization, outlier rejection, and melt temperature (T(m)) estimation--and performs optimally in the presence of triplicate (or higher) sample data. The final output is a report that summarizes the results of a DSF experiment. The goal of Meltdown is not to replace human analysis of the raw fluorescence data but to provide a meaningful and comprehensive interpretation of the data to make this useful experimental technique accessible to inexperienced users, as well as providing a starting point for detailed analyses by more experienced users.