Differential scanning fluorometry signatures as indicators of enzyme inhibitor mode of action: case study of glutathione S-transferase

Cellular thermal shift assay: an approach to identify and assess protein target engagement

INTRODUCTION

A comprehensive and global knowledge of protein target engagement is of vital importance for mechanistic studies and in drug development. Since its initial introduction, the cellular thermal shift assay (CETSA) has proven to be a reliable and flexible technique that can be widely applied to multiple contexts and has profound applications in facilitating the identification and assessment of protein target engagement.

AREAS COVERED

This review introduces the principle of CETSA, elaborates on western blot-based CETSA and MS-based thermal proteome profiling (TPP) as well as the major applications and prospects of these approaches.

EXPERT OPINION

CETSA primarily evaluates a given ligand binding to a particular target protein in cells and tissues with the protein thermal stabilities analyzed by western blot. When coupling mass spectrometry with CETSA, thermal proteome profiling allows simultaneous proteome-wide experiment that greatly increased the efficiency of target engagement evaluation, and serves as a promising strategy to identify protein targets and off-targets as well as protein-protein interactions to uncover the biological effects. The CETSA approaches have broad applications and potentials in drug development and clinical research.

Protein Design Strategies for the Structural–Functional Studies of G Protein-Coupled Receptors

G protein-coupled receptors (GPCRs) are an important family of membrane proteins responsible for many physiological functions in human body. High resolution GPCR structures are required to understand their molecular mechanisms and perform rational drug design, as GPCRs play a crucial role in a variety of diseases. That is difficult to obtain for the wild-type proteins because of their low stability. In this review, we discuss how this problem can be solved by using protein design strategies developed to obtain homogeneous stabilized GPCR samples for crystallization and cryoelectron microscopy.

Synthesis and biological evaluation of thiazolidinedione derivatives with high ligand efficiency to P. aeruginosa PhzS

The thiazolidinone ring is found in compounds that have widespan biology activity and there is mechanism-based evidence that compounds bearing this moiety inhibit P. aeruginosa PhzS (PaPzhS), a key enzyme in the biosynthesis of the virulence factor named pyocyanin. Ten novel thiazolidinone derivatives were synthesised and screened against PaPhzS, using two orthogonal assays. The biological results provided by these and 28 other compounds, whose synthesis had been described, suggest that the dihydroquinazoline ring, found in the previous hit (A- Kd = 18 µM and LE = 0.20), is not required for PaPzhS inhibition, but unsubstituted nitrogen at the thiazolidinone ring is. The molecular simplification approach, pursued in this work, afforded an optimised lead compound (13- 5-(2,4-dimethoxyphenyl)thiazolidine-2,4-dione) with 10-fold improvement in affinity (Kd= 1.68 µM) and more than 100% increase in LE (0.45), which follows the same inhibition mode as the original hit compound (competitive to NADH).Executive summaryPhzS is a key enzyme in the pyocyanin biosynthesis pathway in P. aeruginosa.Orthogonal assays (TSA and FITC) show that fragment-like thiazolidinedione derivatives bind to PaPhzS with one-digit micromolar affinity.Fragment-like thiazolidinedione derivatives bind to the cofactor (NADH) binding site in PaPhzS.The molecular simplification optimised the ligand efficiency and affinity of the lead compound.

Structural Insights into Notum Covalent Inhibition

The carboxylesterase Notum hydrolyzes a palmitoleate moiety from Wingless/Integrated(Wnt) ligands and deactivates Wnt signaling. Notum inhibitors can restore Wnt signaling which may be of therapeutic benefit for pathologies such as osteoporosis and Alzheimer's disease. We report the identification of a novel class of covalent Notum inhibitors, 4-(indolin-1-yl)-4-oxobutanoate esters. High-resolution crystal structures of the Notum inhibitor complexes reveal a common covalent adduct formed between the nucleophile serine-232 and hydrolyzed butyric esters. The covalent interaction in solution was confirmed by mass spectrometry analysis. Inhibitory potencies vary depending on the warheads used. Mechanistically, the resulting acyl-enzyme intermediate carbonyl atom is positioned at an unfavorable angle for the approach of the active site water, which, combined with strong hydrophobic interactions with the enzyme pocket residues, hinders the intermediate from being further processed and results in covalent inhibition. These insights into Notum catalytic inhibition may guide development of more potent Notum inhibitors.

Structural insights into protein folding, stability and activity using in vivo perdeuteration of hen egg-white lysozyme

This structural and biophysical study exploited a method of perdeuterating hen egg-white lysozyme based on the expression of insoluble protein in Escherichia coli followed by in-column chemical refolding. This allowed detailed comparisons with perdeuterated lysozyme produced in the yeast Pichia pastoris, as well as with unlabelled lysozyme. Both perdeuterated variants exhibit reduced thermal stability and enzymatic activity in comparison with hydrogenated lysozyme. The thermal stability of refolded perdeuterated lysozyme is 4.9°C lower than that of the perdeuterated variant expressed and secreted in yeast and 6.8°C lower than that of the hydrogenated Gallus gallus protein. However, both perdeuterated variants exhibit a comparable activity. Atomic resolution X-ray crystallographic analyses show that the differences in thermal stability and enzymatic function are correlated with refolding and deuteration effects. The hydrogen/deuterium isotope effect causes a decrease in the stability and activity of the perdeuterated analogues; this is believed to occur through a combination of changes to hydrophobicity and protein dynamics. The lower level of thermal stability of the refolded perdeuterated lysozyme is caused by the unrestrained Asn103 peptide-plane flip during the unfolded state, leading to a significant increase in disorder of the Lys97-Gly104 region following subsequent refolding. An ancillary outcome of this study has been the development of an efficient and financially viable protocol that allows stable and active perdeuterated lysozyme to be more easily available for scientific applications.

A novel scaffold to fight Pseudomonas aeruginosa pyocyanin production: early steps to novel antivirulence drugs

Aim: Although bacterial resistance is a growing concern worldwide, the development of antibacterial drugs has been steadily decreasing. One alternative to fight this issue relies on reducing the bacteria virulence without killing it. PhzS plays a pivotal role in pyocyanin production in Pseudomonas aeruginosa. Results: A total of 31 thiazolidinedione derivatives were evaluated as putative PhzS inhibitors, using thermo shift assays. Compounds that significantly shifted PhzS's Tm had their mode of inhibition (cofactor competitor) and affinity calculated by thermo shift assays as well. The most promising compound (E)-5-(4-((4-oxo-3-phenyl-3,4-dihydroquinazolin-2-yl)methoxy)benzylidene)thiazolidine-2,4-dione had their affinity confirmed by microscale thermophoresis (K_d = 18 μM). Cellular assays suggest this compound reduces pyocyanin production in vitro, but does not affect P. aeruginosa viability. Conclusion: The first inhibitor of PhzS is described.

The application of differential scanning fluorimetry in exploring bisubstrate binding to protein arginine N-methyltransferase 1

Protein arginine N-methyltransferases (PRMTs) are a family of 9 enzymes that catalyze mono- or di-methylation of arginine residues using S-adenosyl-l-methionine (SAM). Arginine methylation is an important post-translational modification that can regulate the activity and structure of target proteins. Altered PRMT activity can lead to a variety of health issues including neurodevelopmental disease, autoimmune disorders, cancer, and cardiovascular disease. Thus, developing a robust mechanistic understanding of PRMT function may provide insight into these various disease states and enable the development of potential therapeutic agents. Although PRMTs have been studied for nearly two decades, a consensus regarding the mechanism of action for this class of enzymes has remained noticeably elusive. To address this shortcoming, differential scanning fluorimetry (DSF) was used to gain mechanistic insight into the order of PRMT substrate and cofactor binding. This methodology confirms that PRMT cofactor binding precedes target substrate binding and supports the use of DSF to study bisubstrate enzymatic reaction mechanisms.

Applications of Differential Scanning Fluorometry and Related Technologies in Characterization of Protein-Ligand Interactions

Differential scanning fluorometry (DSF) is an efficient and high-throughput method to analyze protein stability, as well as detect ligand interactions through perturbations of the protein's melting temperature. The method monitors protein unfolding by observing the fluorescence changes of a sample, whether through an environmentally sensitive fluorophore or by intrinsic protein fluorescence, while a temperature gradient is applied. Here, we describe in detail how to develop and optimize DSF assays to identify protein-ligand interactions while exploring different buffer and additive conditions. Analysis of the data and further applications of the method are also discussed.

Expanding the Plant GSTome Through Directed Evolution: DNA Shuffling for the Generation of New Synthetic Enzymes With Engineered Catalytic and Binding Properties

Glutathione transferases (GSTs, EC. 2.5.1.18) are inducible multifunctional enzymes that are essential in the detoxification and degradation of toxic compounds. GSTs have considerable biotechnological potential. In the present work, a new method for the generation of synthetic GSTs was developed. Abiotic stress treatment of Phaseolus vulgaris and Glycine max plants led to the induction of total GST activity and allowed the creation of a GST-enriched cDNA library using degenerated GST-specific primers and reverse transcription-PCR. This library was further diversified by employing directed evolution through DNA shuffling. Activity screening of the evolved library led to the identification of a novel tau class GST enzyme (PvGmGSTUG). The enzyme was purified by affinity chromatography, characterized by kinetic analysis, and its structure was determined by X-ray crystallography. Interestingly, PvGmGSTUG displayed enhanced glutathione hydroperoxidase activity, which was significantly greater than that reported so far for natural tau class GSTs. In addition, the enzyme displayed unusual cooperative kinetics toward 1-chloro-2,4-dinitrochlorobenzene (CDNB) but not toward glutathione. The present work provides an easy approach for the simultaneous shuffling of GST genes from different plants, thus allowing the directed evolution of plants GSTome. This may permit the generation of new synthetic enzymes with interesting properties that are valuable in biotechnology.

Hot-Spotting with Thermal Scanning: A Ligand- and Structure-Independent Assessment of Target Ligandability

Evaluating the ligandability of a protein target is a key component when defining hit-finding strategies or when prioritize among drug targets. Computational as well as biophysical approaches based on nuclear magnetic resonance (NMR) fragment screening are powerful approaches but suffer from specific constraints that limit their usage. Here, we demonstrate the applicability of high-throughput thermal scanning (HTTS) as a simple and generic biophysical fragment screening method to reproduce assessments from NMR-based screening. By applying this method to a large set of proteins we can furthermore show that the assessment is predictive of the success of high-throughput screening (HTS). The few divergences for targets of low ligandability originate from the sensitivity differences of the orthogonal biophysical methods. We thus applied a new strategy making use of modulations in the solvent structure to improve assay sensitivity. This novel approach enables improved ligandability assessments in accordance with NMR-based assessments and more importantly positions the methodology as a valuable option for biophysical fragment screening.

Molecular and Spectroscopic Characterization of Aspergillus flavipes and Pseudomonas putida L-Methionine γ-Lyase in Vitro

Pseudomonas putida L-methionine γ-lyase (PpMGL) has been recognized as an efficient anticancer agent, however, its antigenicity and stability remain as critical challenges for its clinical use. From our studies, Aspergillus flavipes L-methionine γ-lyase (AfMGL) displayed more affordable biochemical properties than PpMGL. Thus, the objective of this work was to comparatively assess the functional properties of AfMGL and PpMGL via stability of their internal aldimine linkage, tautomerism of pyridoxal 5'-phosphate (PLP) and structural stability responsive to physicochemical factors. The internal Schiff base of AfMGL and PpMGL have the same stability to hydroxylamine and human serum albumin. Acidic pHs resulted in strong cleavage of the internal Schiff base, inducing the unfolding of MGLs, compared to neutral-alkaline pHs. At λ 280 nm excitation, both AfMGL and PpMGL have identical fluorescence emission spectra at λ 335 nm for the intrinsic tryptophan and λ 560 nm for the internal Schiff base. The maximum PLP tautomeric shift of ketoenamine to enolimine was detected at acidic pH causing complete enzyme unfolding, subunits dissociation and tautomeric shift of intrinsic PLP, rather than neutral-alkaline ones. The T _m of AfMGL and PpMGL in presence of thermal stabilizer/ destabilizer was assayed by DSF. The T _m of AfMGL and PpMGL was 73.1 °C and 74.4 °C, respectively, suggesting the higher proximity to the tertiary structure of both enzymes. The T _m of AfMGL and PpMGL was slightly increased by trehalose and EDTA in contrast to guanidine HCl and urea. The active site and PLP-binding domains are identically conserved in both AfMGL and PpMGL.

Biochemical Characterization of the Detoxifying Enzyme Glutathione Transferase P1-1 from the Camel Camelus Dromedarius

Glutathione transferase (GST, EC 2.5.1.18) is a primary line of defense against toxicities of electrophile compounds and oxidative stress and therefore is involved in stress-response and cell detoxification. In the present study, we investigated the catalytic and structural properties of the glutathione transferase (GST) isoenzyme P1-1 from Camelus dromedarius (CdGSTP1-1). Recombinant CdGSTP1-1 was produced in Escherichia coli BL21(DE3) and purified to electrophoretic homogeneity. Kinetic analysis revealed that CdGSTP1-1 displays broad substrate specificity and shows high activity towards halogenated aryl-compounds, isothiocyanates and hydroperoxides. Computation analysis and structural comparison of the catalytic and ligand binding sites of CdGSTP1-1 with other pi class GSTs allowed the identification of major structural variations that affect the active site pocket and the catalytic mechanism., Affinity labeling and kinetic inhibition studies identified key regions that form the ligandin-binding site (L-site) and gave further insights into the mechanism of non-substrate ligand recognition. The results of the present study provide new information into camelid detoxifying mechanism and new knowledge into the diversity and complex enzymatic functions of GST superfamily.

Chaperonin-Based Biolayer Interferometry To Assess the Kinetic Stability of Metastable, Aggregation-Prone Proteins

Stabilizing the folded state of metastable and/or aggregation-prone proteins through exogenous ligand binding is an appealing strategy for decreasing disease pathologies caused by protein folding defects or deleterious kinetic transitions. Current methods of examining binding of a ligand to these marginally stable native states are limited because protein aggregation typically interferes with analysis. Here, we describe a rapid method for assessing the kinetic stability of folded proteins and monitoring the effects of ligand stabilization for both intrinsically stable proteins (monomers, oligomers, and multidomain proteins) and metastable proteins (e.g., low Tm) that uses a new GroEL chaperonin-based biolayer interferometry (BLI) denaturant pulse platform. A kinetically controlled denaturation isotherm is generated by exposing a target protein, immobilized on a BLI biosensor, to increasing denaturant concentrations (urea or GuHCl) in a pulsatile manner to induce partial or complete unfolding of the attached protein population. Following the rapid removal of the denaturant, the extent of hydrophobic unfolded/partially folded species that remains is detected by an increased level of GroEL binding. Because this kinetic denaturant pulse is brief, the amplitude of binding of GroEL to the immobilized protein depends on the duration of the exposure to the denaturant, the concentration of the denaturant, wash times, and the underlying protein unfolding-refolding kinetics; fixing all other parameters and plotting the GroEL binding amplitude versus denaturant pulse concentration result in a kinetically controlled denaturation isotherm. When folding osmolytes or stabilizing ligands are added to the immobilized target proteins before and during the denaturant pulse, the diminished population of unfolded/partially folded protein manifests as a decreased level of GroEL binding and/or a marked shift in these kinetically controlled denaturation profiles to higher denaturant concentrations. This particular platform approach can be used to identify small molecules and/or solution conditions that can stabilize or destabilize thermally stable proteins, multidomain proteins, oligomeric proteins, and, most importantly, aggregation-prone metastable proteins.

Toremifene interacts with and destabilizes the Ebola virus glycoprotein

Ebola viruses (EBOVs) are responsible for repeated outbreaks of fatal infections, including the recent deadly epidemic in West Africa. There are currently no approved therapeutic drugs or vaccines for the disease. EBOV has a membrane envelope decorated by trimers of a glycoprotein (GP, cleaved by furin to form GP1 and GP2 subunits) which is solely responsible for host cell attachment, endosomal entry and membrane fusion1–7. GP is thus a primary target for the development of antiviral drugs. Here we report the first unliganded structure of EBOV GP, and complexes with an anticancer drug toremifene and the painkiller ibuprofen. The high-resolution apo structure gives a more complete and accurate picture of the molecule, and allows conformational changes introduced by antibody and receptor binding to be deciphered8–10. Unexpectedly both toremifene and ibuprofen bind in a cavity between the attachment (GP1) and fusion (GP2) subunits at the entrance to a large tunnel that links with equivalent tunnels from the other monomers of the trimer at the 3-fold axis. Protein-drug interactions, with both GP1 and GP2, are predominately hydrophobic. Residues lining the binding site are highly conserved amongst filoviruses except Marburg virus (MARV), suggesting that MARV may not bind these drugs. Thermal shift assays show up to a 14 °C decrease in protein melting temperature upon toremifene binding, while ibuprofen has only a marginal effect and is a less potent inhibitor. The results suggest that inhibitor binding destabilizes GP and triggers premature release of GP2, therefore preventing fusion between the viral and endosome membranes. Thus these complex structures reveal the mechanism of inhibition and may guide the development of more powerful anti-EBOV drugs.

Optimization of protein samples for NMR using thermal shift assays

Maintaining a stable fold for recombinant proteins is challenging, especially when working with highly purified and concentrated samples at temperatures >20 °C. Therefore, it is worthwhile to screen for different buffer components that can stabilize protein samples. Thermal shift assays or ThermoFluor(®) provide a high-throughput screening method to assess the thermal stability of a sample under several conditions simultaneously. Here, we describe a thermal shift assay that is designed to optimize conditions for nuclear magnetic resonance studies, which typically require stable samples at high concentration and ambient (or higher) temperature. We demonstrate that for two challenging proteins, the multicomponent screen helped to identify ingredients that increased protein stability, leading to clear improvements in the quality of the spectra. Thermal shift assays provide an economic and time-efficient method to find optimal conditions for NMR structural studies.

Inhibition of the recombinant cattle tick Rhipicephalus (Boophilus) annulatus glutathione S-transferase

Rhipicephalus (Boophilus) annulatus is a bloodsucking ectoparasite that causes severe production losses in the cattle industry. This study aims to evaluate the in vitro effects of tannic acid, hematin (GST inhibitors) and different plant extracts (rich in tannic acid) on the activity of the recombinant glutathione S-transferase enzyme of the Egyptian cattle tick R. annulatus (rRaGST), in order to confirm their ability to inhibit the parasitic essential detoxification enzyme glutathione S-transferase. Extraction with 70% ethanol of Hibiscus cannabinus (kenaf flowers), Punica granatum (red and white pomegranate peel), Musa acuminata (banana peel) (Musaceae), Medicago sativa (alfalfa seeds), Tamarindus indicus (seed) and Cuminum cyminum (cumin seed) were used to assess: (i) inhibitory capacities of rRaGST and (ii) their phenolic and flavonoid contents. Ethanol extraction of red pomegranate peel contained the highest content of phenolic compounds (29.95mg gallic acid/g dry tissue) compared to the other studied plant extracts. The highest inhibition activities of rRaGST were obtained with kenaf and red pomegranate peel (P. granatum) extracts with IC50 values of 0.123 and 0.136mg dry tissue/ml, respectively. Tannic acid was the more effective inhibitor of rRaGST with an IC50 value equal to 4.57μM compared to delphinidine-HCl (IC50=14.9±3.1μM). Gossypol had a weak inhibitory effect (IC50=43.7μM), and caffeic acid had almost no effect on tick GST activity. The IC50 values qualify ethacrynic acid as a potent inhibitor of rRaGST activity (IC50=0.034μM). Cibacron blue and hematin showed a considerable inhibition effect on rRaGST activity, and their IC50 values were 0.13μM and 7.5μM, respectively. The activity of rRaGST was highest for CDNB (30.2μmol/min/mg protein). The enzyme had also a peroxidatic activity (the specific activity equals 26.5μmol/min/mg protein). Both tannic acid and hematin inhibited rRaGST activity non-competitively with respect to GSH and competitively with respect to CDNB. While red pomegranate extracts inhibited rRaGST activity competitively with respect to GSH, uncompetitive inhibition was observed with respect to CDNB.

Structural and regulatory elements of HCV NS5B polymerase--β-loop and C-terminal tail--are required for activity of allosteric thumb site II inhibitors

Elucidation of the mechanism of action of the HCV NS5B polymerase thumb site II inhibitors has presented a challenge. Current opinion holds that these allosteric inhibitors stabilize the closed, inactive enzyme conformation, but how this inhibition is accomplished mechanistically is not well understood. Here, using a panel of NS5B proteins with mutations in key regulatory motifs of NS5B – the C-terminal tail and β-loop – in conjunction with a diverse set of NS5B allosteric inhibitors, we show that thumb site II inhibitors possess a distinct mechanism of action. A combination of enzyme activity studies and direct binding assays reveals that these inhibitors require both regulatory elements to maintain the polymerase inhibitory activity. Removal of either element has little impact on the binding affinity of thumb site II inhibitors, but significantly reduces their potency. NS5B in complex with a thumb site II inhibitor displays a characteristic melting profile that suggests stabilization not only of the thumb domain but also the whole polymerase. Successive truncations of the C-terminal tail and/or removal of the β-loop lead to progressive destabilization of the protein. Furthermore, the thermal unfolding transitions characteristic for thumb site II inhibitor – NS5B complex are absent in the inhibitor – bound constructs in which interactions between C-terminal tail and β-loop are abolished, pointing to the pivotal role of both regulatory elements in communication between domains. Taken together, a comprehensive picture of inhibition by compounds binding to thumb site II emerges: inhibitor binding provides stabilization of the entire polymerase in an inactive, closed conformation, propagated via coupled interactions between the C-terminal tail and β-loop.

Discrimination of potent inhibitors of Toxoplasma gondii enoyl-acyl carrier protein reductase by a thermal shift assay

Many microbial pathogens rely on a type II fatty acid synthesis (FASII) pathway that is distinct from the type I pathway found in humans. Enoyl-acyl carrier protein reductase (ENR) is an essential FASII pathway enzyme and the target of a number of antimicrobial drug discovery efforts. The biocide triclosan is established as a potent inhibitor of ENR and has been the starting point for medicinal chemistry studies. We evaluated a series of triclosan analogues for their ability to inhibit the growth of Toxoplasma gondii, a pervasive human pathogen, and its ENR enzyme (TgENR). Several compounds that inhibited TgENR at low nanomolar concentrations were identified but could not be further differentiated because of the limited dynamic range of the TgENR activity assay. Thus, we adapted a thermal shift assay (TSA) to directly measure the dissociation constant (Kd) of the most potent inhibitors identified in this study as well as inhibitors from previous studies. Furthermore, the TSA allowed us to determine the mode of action of these compounds in the presence of the reduced nicotinamide adenine dinucleotide (NADH) or nicotinamide adenine dinucleotide (NAD⁺) cofactor. We found that all of the inhibitors bind to a TgENR-NAD⁺ complex but that they differed in their dependence on NAD⁺ concentration. Ultimately, we were able to identify compounds that bind to the TgENR-NAD⁺ complex in the low femtomolar range. This shows how TSA data combined with enzyme inhibition, parasite growth inhibition data, and ADMET predictions allow for better discrimination between potent ENR inhibitors for the future development of medicine.

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

A simple, inexpensive, and universal method to quantify the recombinant proteins in Escherichia coli cell lysate using differential scanning fluorimetry (DSF) is reported. This method is based on the precise correlation between Δ(fluorescence intensity) determined by DSF and the amount of protein in solution. We first demonstrated the effectiveness of the DSF method using two commercially available enzymes, α-amylase and cellobiase, and then confirmed its utility with two recombinant proteins, amylosucrase and maltogenic amylase, expressed in E. coli. The Δ(fluorescence intensity) in DSF analysis accurately correlated with the concentration of the purified enzymes as well as the recombinant proteins in E. coli cell lysates. The main advantage of this method over other techniques such as Western blotting, enzyme-linked immunosorbent assay (ELISA), and green fluorescence protein (GFP) fusion proteins is that intact recombinant protein can be quantified without the requirement of additional chemicals or modifications of the recombinant protein. This DSF assay can be performed using widely available equipment such as a real-time polymerase chain reaction (RT-PCR) instrument, microplates or microtubes, and fluorescent dye. This simple but powerful method can be easily applied in a wide range of research areas that require quantification of expressed recombinant proteins.

Recent developments in the use of differential scanning fluorometry in protein and small molecule discovery and characterization

INTRODUCTION

Despite tremendous advances in the application of biophysical methods in drug discovery, the preponderance of instruments and techniques still require sophisticated analyses by dedicated personnel and/or large amounts of frequently hard-to-produce proteins. A technique which carries the promise of simplicity and relatively low protein consumption is the differential scanning fluorometry (DSF). This technique monitors protein through the use of environmentally sensitive fluorescent dye, in a temperature-ramp regime by observing the gradual exposure to the solvent of otherwise buried hydrophobic faces of protein domains.

AREAS COVERED

This review describes recent developments in the field of DSF. This article pays a particular emphasis on the advances published during the 2010 - 2013 period.

EXPERT OPINION

There has been a significant diversification of DSF applications beyond initial small molecule discovery into areas such as protein therapeutic development, formulation studies and various mechanistic investigations. This serves as a further indication of the broad penetration of the technique. In the small molecule arena, DSF has expanded toward sophisticated co-dependency MOA tests, demonstrating the wealth of information which the technique can provide. Importantly, the first public deposition of a large screening dataset may enable the use of thermal stabilization data in refining in silico models for small molecule binding.