Microscale thermophoresis in the investigation of biomolecular interactions

Accurate characterization of the interactions between biomolecules not only provides fundamental insights into cellular processes but also paves the way for drug discovery and development. With recent increases in throughput and sensitivity, biophysical technologies have become prominent tools for studying biomolecular interactions. Biophysical techniques that can reduce costs, shorten detection time, simplify the complexity of the system under analysis, and simultaneously provide high-quality data content are particularly favored. Here, we summarize the qualitative and quantitative analysis of biomolecular interactions using Micro Scale Thermophoresis(MST), as well as extend the application of MST functions to explore thermodynamics, enzyme kinetics and protein folding-unfolding processes. MST has emerged as a simple and powerful biophysical approach for identifying and quantifying binding events based on the movement of molecules along microscopic temperature gradients. The advantages of MST over other competitive biophysical techniques include freedom from immobilization, rapid analysis times, lower sample consumption, and the ability to analyze binding affinities in cell lysates. This article discusses the instrumental setups, principles, experimental workflows, and examples of MST application in practice.

Amplified Immunoassay of Human IgG Using Real-time Biomolecular Interaction Analysis (BIA) Technology

An automated biomolecular interaction analysis instrument (BIAcore) based on surface plasmon resonance (SPR) has been used to determine human immunoglobulin G (IgG) in real time. Polyclonal anti human IgG antibody was covalently immobilized to a carboxymethyldextran modified gold film surface. The samples of human IgG prepared in HBS buffer were poured over the immobilized surface. The signal amplification antibody was applied to amplify the response signal. After each measurement, the surface was regenerated with 0.1 mol/L H 3PO 4. The assay was rapid, requiring only 30 min for antibody immobilization and 20 min for each subsequent process of immune binding, antibody amplification and regeneration. The antibody immobilized surface had good response to human IgG in the range of 0.12 -60 nmol/L with a detection limit of 60 pmol/L. The same antibody immobilized surface could be used for more than 110 cycles of binding, amplification and regeneration. The results demonstrate that the sensitivity, specificity and reproducibility of amplified immunoassay using real time BIA technology are satisfactory.

Study on specific interaction of new ferrocene-substituted carborane conjugates with hemoglobin protein

The interactions between the new organometallic complexes, ferrocenesubstituted dithioocarborane conjugates （denoted as FcSB1, FcSB2 and FcSBCO） and hemoglobin （Hb） are investigated by electrochemistry, fluorescence and UVvis absorption spectroscopy. The results demonstrate that FcSB1, FcSB2 and FcSBCO can bind to the heme iron center through the replacement of the weakly bound H20/02 in the distal heme pocket of Hb by their sulfur donor atoms, inducing the allosteric change from the R state （oxygenated conformation, relax） to T state （deoxygenated conformation, tense）. The binding affinity is in the order of FcSBCO〉FeSB2〉FeSB1. Moreover, the fluorescence study illustrates that the three ferrocenecarborane conjugates differently affect the quarterly and tertiary structures as well as the polarity in the surrounding of the Trp and Tyr residues in Hb. Typically, FcSB2 mainly induces alterations of the microenvironment around the 1337Trp residue which is located on the cql32 interface of Hb. Such distinct influences are attributed to the structural features of FcSB1, FcSB2 and FcSBCO containing hydrophobic ferrocenyl and carboranyl units as well as C=O group. Screening the proteinbinding behavior can signify the potential bioactivity of such molecules and may be helpful in the future development of promising multifunctional metallodrugs.

SURFACE STRESS PROPERTIES OF DNA-MICROCANTILEVER SYSTEMS

For the first time, the connection between surface stress and nanoscopic interac- tions of DNA adsorbed on microcantilever is established by combining Strey＇s mesoscopic liquid crystal theory and Stoney＇s formula. It is shown that surface stress depends not only on biomolec- ular interactions of DNA biofilm but also on mechanical properties of cantilever. Considering the correlativity between grafting density and chain length of DNA chain, we discuss the differences between DNA-microcantilever system and DNA solution system. The major theoretical achieve- ment of this model is to identify the main contributions to surface stress under different detection conditions. This provides guidelines for designing new biosensors with high sensitivity and improved reliability.