Noncovalent Complexes Research Articles

High selectivity of the hyperthermophilic subtilase propeptide domain toward inhibition of its cognate protease.

Microbial extracellular subtilases are highly active proteolytic enzymes commonly used in commercial applications. These subtilases are synthesized in their inactive proform, which matures into the active protease under the control of the propeptide domain. In mesophilic bacterial prosubtilases, the propeptide functions as both an obligatory chaperone and an inhibitor of the subtilase catalytic domain. In contrast, the propeptides of hyperthermophilic archaeal prosubtilases act mainly as tight inhibitors and are not essential for subtilase folding. It is unclear whether this stronger inhibitory activity of hyperthermophilic propeptides results in their higher selectivity toward their cognate subtilases, in contrast to promiscuous mesophilic propeptides. Here, we showed that the propeptide of pernisine, a hyperthermostable archaeal subtilase, strongly interacts with and inhibits pernisine, but not the homologous subtilisin Carlsberg and proteinase K. Instead, the pernisine propeptide was readily degraded by subtilisin Carlsberg and proteinase K. In addition, the catalytic domain of unprocessed propernisine was also susceptible to degradation but became proteolytically stable after autoprocessing of propernisine into the inactive, noncovalent complex propeptide:pernisine. This allowed efficient transactivation of the autoprocessed complex propeptide:pernisine through degradation of pernisine propeptide by subtilisin Carlsberg and proteinase K at mesophilic temperature. Moreover, we demonstrated that active pernisine molecules are inhibited by the propeptide that is released after pernisine-catalyzed degradation of the unprocessed propernisine catalytic domain. This highlights the high inhibitory potency of the hyperthermophilic propeptide toward its cognate subtilase and its importance in regulating subtilase maturation, to prevent the degradation of the unprocessed subtilase precursors by the prematurely activated molecules. IMPORTANCE Many microorganisms secrete proteases into their environment to degrade protein substrates for their growth. The important group of these extracellular enzymes are subtilases, which are also widely used in practical applications. These subtilases are inhibited by their propeptide domain, which is degraded during the prosubtilase maturation process. Here, we showed that the propeptide of pernisine, a prion-degrading subtilase from the hyperthermophilic archaeon, strongly inhibits pernisine with extraordinarily high binding affinity. This interaction proved to be highly selective, as pernisine propeptide was rapidly degraded by mesophilic pernisine homologs. This in turn allowed rapid transactivation of propernisine by mesophilic subtilases at lower temperatures, which might simplify the procedures for preparation of active pernisine for commercial use. The results reported in this study suggest that the hyperthermophilic subtilase propeptide evolved to function as tight and selective regulator of maturation of the associated prosubtilase to prevent its premature activation under high temperatures.

Changes in Hemoglobin Properties in Complex with Glutathione and after Glutathionylation.

Hemoglobin is the main protein of red blood cells that provides oxygen transport to all cells of the human body. The ability of hemoglobin to bind the main low-molecular-weight thiol of the cell glutathione, both covalently and noncovalently, is not only an important part of the antioxidant protection of red blood cells, but also affects its affinity for oxygen in both cases. In this study, the properties of oxyhemoglobin in complex with reduced glutathione (GSH) and properties of glutathionylated hemoglobin bound to glutathione via an SS bond were characterized. For this purpose, the methods of circular dichroism, Raman spectroscopy, infrared spectroscopy, tryptophan fluorescence, differential scanning fluorimetry, and molecular modeling were used. It was found that the glutathionylation of oxyhemoglobin caused changes in the secondary structure of the protein, reducing the alpha helicity, but did not affect the heme environment, tryptophan fluorescence, and the thermostability of the protein. In the noncovalent complex of oxyhemoglobin with reduced glutathione, the secondary structure of hemoglobin remained almost unchanged; however, changes in the heme environment and the microenvironment of tryptophans, as well as a decrease in the protein's thermal stability, were observed. Thus, the formation of a noncovalent complex of hemoglobin with glutathione makes a more significant effect on the tertiary and quaternary structure of hemoglobin than glutathionylation, which mainly affects the secondary structure of the protein. The obtained data are important for understanding the functioning of glutathionylated hemoglobin, which is a marker of oxidative stress, and hemoglobin in complex with GSH, which appears to deposit GSH and release it during deoxygenation to increase the antioxidant protection of cells.

Formation and microstructural characterization of scallop (Patinopecten yessoensis) male gonad hydrolysates/sodium alginate coacervations as a function of pH

Studying the noncovalent interactions between proteins and polysaccharides is quite important mainly due to the wide number of applications such as developing pH-responsive complexes. Scallop Patinopecten yessoensis male gonad hydrolysates‑sodium alginate (SMGHs-SA) was investigated as noncovalent complexes at pH from 1 to 10. The critical pH values pHC (around 6) and pHφ (around 4) were independent of the SMGHs-SA ratio, indicating the formation of soluble and insoluble complexes. The pH response of SMGHs-SA complexes was evaluated by investigating the rheological behavior, moisture distribution, functional group change and microstructure. Compared to the co-soluble and soluble complexes phases, the SMGHs-SA complexes had a higher storage modulus and viscosity as well as a lower relaxation time (T23) in the insoluble complexes phase (pHφ>3). Additionally, the amide I band and COO− stretching vibration peaks were redshifted and the amide A band vibration peaks were blueshifted by acidification. Electrostatic interactions and intermolecular/intramolecular hydrogen bonding led to SMGHs-SA agglomeration at pH 3, forming a uniform and dense gel network structure with strong gel strength and water-retention capacity. This study provides a theoretical and methodological basis for the design of novel pH-responsive complexes by studying SMGHs-SA complex coacervation.

Combination and precipitation mechanism of soy protein and tea polyphenols

Non-covalent interactions of plant proteins and polyphenols is often occurred in food production and processing. However, the combination of the two may form a precipitate to reduce the aesthetic value and taste. In this study, we prepared different proportions of soy protein isolate (SPI) and catechin/epigallocatechin-3-gallate (EGCG) non-covalent complexes. The structural and conformational changes of the complex in the non-covalent interaction system were explored by multi-spectral technology, and the transition mechanism from the solution-state to the precipitation-state was analyzed. As a “bridge”, polyphenols made more SPI cross-linked and aggregate, and reduce hydrophobicity. The enhancement of resonance Rayleigh scattering further confirmed the formation of macromolecular particles. SPI mainly combined with catechin/EGCG through hydrogen bonds, and more benzene rings and phenol hydroxyl structure of EGCG were conducive to the formation of a more stable complex with protein. In addition, the increase of polyphenol concentration promoted the conjugation effect (hydrophobic interaction and electrostatic interaction) with protein, resulting in insoluble high molecular weight aggregate precipitation.

Alternative Chromophore Binding Sites in Noncovalent Fluorescent Complexes of Bacterial Lipocalin

Alternative Chromophore Binding Sites in Noncovalent Fluorescent Complexes of Bacterial Lipocalin

Microfluidization of soybean protein isolate-tannic acid complex stabilized emulsions: Characterization of emulsion properties, stability and in vitro digestion properties

Emulsion stability and sustained-release can be improved with a non-covalent complexing of a soybean protein isolate (SPI) with -tannic acid (TA) and dynamic high-pressure microfluidization (DHPM). The microstructure, physicochemical properties, and interfacial properties were investigated. The properties of the DHPM-treated emulsions were improved significantly, with the 120 MPa DHPM-treated SPI-TA emulsion (SPI-TA 120) having the best microstructure. The highest interface protein content, viscosity and viscoelasticity at 120 MPa of pressure facilitated the stability of the emulsion. The oxidation kinetics of emulsions was established. It was demonstrated that the oxidation stability of SPI-TA 120 was higher than SPI and SPI-TA emulsions without DHPM treatment. In addition, DHPM-treated SPI-TA emulsions showed the most positive effect on the slow release of curcumin compared to the control group. The formation of non-covalent protein complexes with polyphenols and DHPM treatment effectively increases the stability of emulsions.

Combining multi–spectroscopy analysis and interfacial properties to research the effect of ultrasonic treatment on soybean protein isolate–tannic acid complexes

In this study, ultrasonic treatment of soybean protein isolate (SPI)–tannic acid (TA) non-covalent complexes were performed. In the multi-spectroscopic analysis, it was found that the content of the α-helix decreased, the exposure of amino acid residues increased, the content of the trans-gauche-trans mode of disulfide bonds increased, and the fluorescence intensity decreased. Static quenching occurred between TA and SPI, and ultrasonic treatment promoted their combination. The SPI–TA complexes had lower surface roughness at 450 W. At this moment, the volume mean diameter and zeta potential of the complexes were 70.76 nm and −22.4 eV, respectively. The surface hydrophobicity, solubility, contact angle, emulsification activity index, and emulsion stability index were 4,355, 73.2%, 49.71°, 117 m2/g, and 63 min, respectively. The diffusion rate of the sample under ultrasonic treatment at 450 W was 0.14777. Low-field nuclear magnetic resonance analysis revealed a higher percentage of immobilized water in the SPI–TA complex at 450 W. The above findings will help to promote the improvement in various aspects of the properties of SPI and enhance its application prospects.

Cyclodextrins and Their Derivatives as Drug Stability Modifiers.

Cyclodextrins (CDs) are cyclic oligosaccharides that contain a relatively hydrophobic central cavity and a hydrophilic outer surface. They are widely used to form non-covalent inclusion complexes with many substances. Although such inclusion complexes typically exhibit higher aqueous solubility and chemical stability than pure drugs, it has been shown that CDs can promote the degradation of some drugs. This property of stabilizing certain drugs while destabilizing others can be explained by the type of CD used and the structure of the inclusion complex formed. In addition, the ability to form complexes of CDs can be improved through the addition of suitable auxiliary substances, forming multicomponent complexes. Therefore, it is important to evaluate the effect that binary and multicomponent complexes have on the chemical and physical stability of complexed drugs. The objective of this review is to summarize the studies on the stabilizing and destabilizing effects of complexes with CDs on drugs that exhibit stability problems.

How Good Are Current Docking Programs at Nucleic Acid-Ligand Docking? A Comprehensive Evaluation.

Nucleic acid (NA)-ligand interactions are of paramount importance in a variety of biological processes, including cellular reproduction and protein biosynthesis, and therefore, NAs have been broadly recognized as potential drug targets. Understanding NA-ligand interactions at the atomic scale is essential for investigating the molecular mechanism and further assisting in NA-targeted drug discovery. Molecular docking is one of the predominant computational approaches for predicting the interactions between NAs and small molecules. Despite the availability of versatile docking programs, their performance profiles for NA-ligand complexes have not been thoroughly characterized. In this study, we first compiled the largest structure-based NA-ligand binding data set to date, containing 800 noncovalent NA-ligand complexes with clearly identified ligands. Based on this extensive data set, eight frequently used docking programs, including six protein-ligand docking programs (LeDock, Surflex-Dock, UCSF Dock6, AutoDock, AutoDock Vina, and PLANTS) and two specific NA-ligand docking programs (rDock and RLDOCK), were systematically evaluated in terms of binding pose and binding affinity predictions. The results demonstrated that some protein-ligand docking programs, specifically PLANTS and LeDock, produced more promising or comparable results compared with the specialized NA-ligand docking programs. Among the programs evaluated, PLANTS, rDock, and LeDock showed the highest performance in binding pose prediction, and their top-1 and best root-mean-square deviation (rmsd) success rates were as follows: PLANTS (35.93 and 76.05%), rDock (27.25 and 72.16%), and LeDock (27.40 and 64.37%). Compared with the moderate level of binding pose prediction, few programs were successful in binding affinity prediction, and the best correlation (Rp = -0.461) was observed with PLANTS. Finally, further comparison with the latest NA-ligand docking program (NLDock) on four well-established data sets revealed that PLANTS and LeDock outperformed NLDock in terms of binding pose prediction on all data sets, demonstrating their significant potential for NA-ligand docking. To the best of our knowledge, this study is the most comprehensive evaluation of popular molecular docking programs for NA-ligand systems.

Combined System for the Simultaneous Delivery of Levofloxacin and Rifampicin: Structural and Functional Properties and Antibacterial Activity.

The therapy of resistant forms of tuberculosis requires the simultaneous use of several drugs, in particular, a combination of rifampicin and levofloxacin. In this paper, we aimed to design a combined system for the simultaneous delivery of these drugs for potential inhalation administration. A feature of this system is the incorporation of rifampicin into optimized liposomal vesicles capable of forming a multipoint non-covalent complex with chitosan-β-cyclodextrin conjugates. Levofloxacin is incorporated into cyclodextrin tori by forming a host-guest complex. Here, a comprehensive study of the physicochemical properties of the obtained systems was carried out and special attention was paid to the kinetics of cargo release for individual drugs and in the combined system. The release of levofloxacin in combined system is slow and is described by the Higuchi model in all cases. The release of rifampicin from liposomes during the formation of complexes with polymeric conjugates is characterized by the change of the Higuchi model to the Korsmeyer-Peppas model with the main type of diffusion against Fick's law. Microbiological studies in solid and liquid growth media a consistently high antibacterial activity of the obtained systems was shown against B. subtilis and E. coli.

Mechanochemical Mediated Coexistence of B←N Coordination and Hydrogen Bonding.

Mechanochemistry afforded a photoactive cocrystal via coexisting (B)O-H⋅⋅⋅N hydrogen bonds and B←N coordination. Specifically, solvent-free mechanochemical ball mill grinding and liquid-assisted grinding of a boronic acid and an alkene resulted in mixtures of hydrogen-bonded and coordinated complexes akin to mixtures of noncovalent complexes that can be obtained in solution in equilibria processes. The alkenes of the hydrogen-bonded assembly undergo an intermolecular [2+2] photodimerization in quantitative conversion, effectively reporting the outcome of the self-assembly processes. Our results suggest that interplay involving noncovalent bonds subjected to mechanochemical conditions can lead to functional solids where, in the current case, the structure composed of the weaker hydrogen bonding interactions predominates.

Mechanochemical Mediated Coexistence of B←N Coordination and Hydrogen Bonding

AbstractMechanochemistry afforded a photoactive cocrystal via coexisting (B)O−H⋅⋅⋅N hydrogen bonds and B←N coordination. Specifically, solvent‐free mechanochemical ball mill grinding and liquid‐assisted grinding of a boronic acid and an alkene resulted in mixtures of hydrogen‐bonded and coordinated complexes akin to mixtures of noncovalent complexes that can be obtained in solution in equilibria processes. The alkenes of the hydrogen‐bonded assembly undergo an intermolecular [2+2] photodimerization in quantitative conversion, effectively reporting the outcome of the self‐assembly processes. Our results suggest that interplay involving noncovalent bonds subjected to mechanochemical conditions can lead to functional solids where, in the current case, the structure composed of the weaker hydrogen bonding interactions predominates.

Development and Characterization of Cationic Nanostructured Lipid Carriers as Drug Delivery Systems for miRNA-27a.

Although miRNA-27a has been identified as a promising candidate for miRNA mimic therapy of obesity, its application is limited due to enzymatic degradation and low membrane permeation. To overcome these problems, we developed cationic nanostructured lipid carriers (cNLCs) using high-pressure homogenization and used them as non-viral carriers for the anti-adipogenic miRNA-27a. Cargo-free octadecylamine-containing NLCs and miRNA/cNLC complexes were characterized regarding particle size, size distributions, zeta potential, pH values, particle topography and morphology, and entrapment efficacy. Furthermore, the cytotoxicity and cellular uptake of the miRNA/cNLC complex in the 3T3-L1 cell line were investigated. The investigation of the biological effect of miRNA-27a on adipocyte development and an estimation of the accumulated Oil-Red-O (ORO) dye in lipid droplets in mature adipocytes were assessed with light microscopy and absorbance measurements. The obtained data show that cNLCs represent a suitable DDS for miRNAs, as miRNA/cNLC particles are rapidly formed through non-covalent complexation due to electrostatic interactions between both components. The miRNA-27a/cNLC complex induced an anti-adipogenic effect on miRNA-27a by reducing lipid droplet accumulation in mature adipocytes, indicating that this approach might be used as a new therapeutic strategy for miRNA mimic replacement therapies in the prevention or treatment of obesity and obesity-related disorders.

Determination of the Dissociation Constant for Polyvalent Receptors Using ELISA: A Case of M13 Phages Displaying Troponin T-Specific Peptides.

Phage-derived affinity peptides have become widespread thanks to their easy selection via phage display. Interactions between a target protein and its specific peptide are similar to those between antibodies and antigens. The strength of these non-covalent complexes may be described by the dissociation constant (Kd). In this paper, protein-specific peptides are exposed on the pIII protein present in the M13 bacteriophage virion with up to five copies. Therefore, one phage particle can bind from one to five ligands. Here, we discuss the dependences between phage-displayed peptides and their ligands in solution using a model system based on troponin T (TnT) binding phages. Moreover, a method of calculating Kd values from ELISA experiments was developed and is presented. The determined Kd values are in the picomolar range.

Mass spectrometry study of ascorbyl palmitate as an agent for nanosomes formation

Background. Study of properties and intermolecular interactions of biologically active compounds which can be used for the purposes of transmembrane drugs delivery is a topical task of modern molecular biophysics. Ascorbyl Palmitate (AP) as a fat-soluble form of vitamin C has recently attracted attention as a promising agent for formation of nanosomes for the “fat insoluble” drug molecules transfer through membranes. However, AP is not sufficiently characterized by up-to-date soft ionization mass spectrometric techniques. Objectives. The aim of the present work is to characterize AP and its intermolecular interactions by a number of mass spectrometric techniques: Electrospray Ionization (ESI), Laser Desorption/Ionization (LDI) and Matrix-Assisted Laser Desorption/Ionization (MALDI). The comparison of these techniques applicability to the study of AP intermolecular interactions as a drug delivery assisting agent is scheduled. Methods. ESI mass spectra are obtained with triple quadrupole Micromass Quattro mass spectrometer. LDI and MALDI experiments are performed by Autoflex II mass spectrometer. Results. In the ESI experiments in the positive ion mode abundant peaks of protonated and cationized AP molecules as well as the peaks of AP clusters nAP•H+ and nAP•Na+ (n=2÷4) are revealed in the mass spectra. This result testifies to the formation of stable noncovalent complexes of the AP molecules in the polar media and confirms the AP ability of formation nanosomes for drug delivery. Analysis of LDI and MALDI mass spectra of AP in positive and negative ion modes shows that in the presence of molecular ions of AP, the peaks of AP dimers or larger AP clusters are not recorded. The ESI probing of the model system containing AP and dipalmitoylphosphatidylcholine (DPPC) reveals stable AP•DPPC•H+ complex which models the AP intermolecular interactions with the phospholipid components of biomembranes and/or liposomes under AP functioning as a drug delivery assisting agent. Conclusions. The current study demonstrates the applicability of all tested mass spectrometric techniques for AP identification in solutions and solid phase, while for the purpose of examining of the AP noncovalent complexes formation and study of AP interactions with biomolecules the ESI is defined as the most effective technique.

Comparative Evaluation of the Pharmacological Activity of Fatty Aromatic Amides and Amines with a Framework Moiety and Their Non-Covalent Complexes

Comparative Evaluation of the Pharmacological Activity of Fatty Aromatic Amides and Amines with a Framework Moiety and Their Non-Covalent Complexes

Determination of HER2 binding domain in antigen-antibody complexes based on chemical crosslinking mass spectrometry

Chemical crosslinking (XL) of non-covalent antigen-antibody complexes followed by mass spectrometric identification (MS) of inter-protein crosslinks can provide spatial constraints between relevant residues, which are valuable structural information associated with the molecular binding interface. To highlight the potential of XL/MS in the biopharmaceutical industry, we herein developed and validated an XL/MS workflow that employed a zero-length linker, 1,1′‑carbonyldiimidazole (CDI), and a widely used medium-length linker, disuccinimidyl sulfoxide (DSSO), for fast, accurate determination of antigen domains targeted by therapeutic antibodies. To avoid false identification, system suitability samples and negative samples were designed for all experiments, and all tandem mass spectra were manually examined. To validate the proposed XL/MS workflow, two complexes involving human epidermal growth factor receptor 2 Fc fusion protein (HER2Fc) with known crystal structures, including HER2Fc-pertuzumab and HER2Fc-trastuzumab, have been subjected to CDI and DSSO crosslinking. Crosslinks established by CDI and DSSO between HER2Fc and pertuzumab accurately revealed their interaction interface. CDI crosslinking contributes more than DSSO because of its short spacer arm and high reactivity towards hydroxyl groups, demonstrating its capacity in protein interaction analysis. The correct binding domain cannot be revealed solely based on DSSO in the HER2Fc-trastuzumab complex, because domain proximity revealed by this 7-atom spacer linker cannot be directly translated as binding interfaces. As the first successful XL/MS application in early-stage therapeutic antibody discovery, we analyzed the molecular binding interface between HER2Fc and H-mab, an innovant drug candidate whose paratopes have not been studied yet. We predict that H-mab probably targets HER2 Domain I. The proposed XL/MS workflow can serve as an accurate, fast, and low-cost method to study the interaction between antibodies and large multi-domain antigens. SignificanceThis article described a fast, low-consumption approach based on chemical crosslinking mass spectrometry (XL/MS) using two linkers for binding domain determination in multidomain antigen-antibody complexes. Our results highlighted the higher importance of zero-length crosslinks established by CDI than 7-atom DSSO crosslinks, as residue proximity revealed by zero-length crosslinks is closely related to epitope-paratope interaction surfaces. Furthermore, the higher reactivity of CDI towards hydroxyl groups broadens the ranges of possible crosslinks, despite the necessity of delicate operation in CDI crosslinking. We suggest that all established CDI and DSSO crosslinks should be comprehensively considered for correct binding domain analysis because predictions solely based on DSSO might be ambiguous. We have determined the binding interface in the HER2-H-mab using CDI and DSSO, which is the first successful application of XL/MS in real-world early-stage biopharmaceutical development.

Basis set customization for modeling noncovalent interactions

AbstractIn this article, a simple approach is proposed to reduce the basis set requirement for computing accurate interaction energies for bimolecular noncovalent complexes. A distributed multipole expansion is used to estimate the importance of basis functions in a given atom. Moderate truncation of basis sets results in reduced computational cost without compromising the accuracy. The approach was found fruitful for wavefunction‐based methods and density functional theory approximation using the Dunning, Karlsruhe, and Jensen basis sets.

Synergistic modification of structural and functional characteristics of whey protein isolate by soybean isoflavones non-covalent binding and succinylation treatment: A focus on emulsion stability

This investigation explored the structural and functional characteristics of whey protein isolate (WPI) and succinylated whey protein isolate (SAn-WPI) modified by varying concentrations (0.25, 0.5, 1.0, 2.0 mg/mL) of soybean isoflavones (SI) through non-covalent interactions. The results of SDS-PAGE and total phenolic contents confirmed the formation of non-covalent complexes. Molecular docking techniques, Fourier-transform infrared spectroscopy, and thermodynamic parameters obtained from fluorescence spectra revealed that non-covalent binding to SI primarily occurs through hydrophobic interactions and hydrogen bonding. Additionally, multispectroscopic techniques demonstrated that succinylation treatment resulted in partial unfolding of the proteins. This led to increased protein flexibility, exposing more binding sites and facilitating the binding between the proteins and SI. Therefore, SAn-WPI/SI exhibits stronger fluorescence quenching ability, antioxidant activity, and emulsifying property compared to WPI/SI at the same SI concentration. The findings illustrate the synergistic effect of non-covalent binding to SI and succinylation treatment on the WPI molecules, thereby promoting the utilization of protein-polyphenol complexes in food emulsion systems.

Molecular Electrostatic Potential Topology Analysis of Noncovalent Interactions.

ConspectusThe topology of molecular electrostatic potential (MESP), V(r), derived from a reliable quantum chemical method has been used as a powerful tool for the study of intermolecular noncovalent interactions. The MESP topology mapping is achieved by computing both ∇V(r) data and the elements of the Hessian matrix at ∇V(r) = 0, the critical point. MESP minimum (Vmin) as well as MESP at a reaction center, specific to an atom (Vn), have been employed as electronic parameters to interpret the variations in the reactivity (activation/deactivation) of chemical systems with respect to the influence of substituents, ligands, π-conjugation, aromaticity, trans influence, hybridization effects, steric effects, cooperativity, noncovalent interactions, etc. In this Account, several studies involving MESP topology analysis, which yielded interpretations of various noncovalent interactions and also provided new insights in the area of chemical bonding, are highlighted. The existence of lone pairs in molecules is distinctly reflected by the topology features of the MESP minima (Vmin). The Vmin is able to probe lone pairs in molecules, and it has been used as a reliable electronic parameter to assess their σ-donating power. Furthermore, MESP topology analysis can be used to forecast the structure and energetics of lone pair π-complexes. The MESP approach to rationalize lone pair interactions in molecular systems has led to the design of cyclic imines for CO2 capture. The MESP topology analysis of intermolecular complexes revealed a hitherto unknown phenomenon in chemical bonding theory─formation of a covalent bond due to the influence of a noncovalent bond. The MESP-guided approach to intermolecular interactions provided a successful design strategy for the development of CO2 capture systems. The MESP parameters Vmin and MESP at the nucleus, Vn, derived for the molecular systems have been used as powerful measures for the extent of electron donor-acceptor (eDA) interactions in noncovalent complexes. Noncovalent bond formation leads to more negative MESP at the acceptor nucleus (VnA) and less negative MESP at the donor nucleus (VnD). The strong linear relationship observed between ΔΔVn = ΔVnD - ΔVnA and bond energy suggested that MESP data provide a clear evidence of bond formation. Furthermore, MESP topology studies established a cooperativity rule for understanding the donor-acceptor interactive behavior of a dimer D...A with a third molecule. According to this, the electron reorganization in the dimer due to the eDA interaction enhances electron richness at "A", the acceptor, and enhances electron deficiency at "D", the donor. Resultantly, D in D...A is more accepting toward trimer formation, while A in D...A is more donating. MESP topology offers promising design strategies to tune the electron-donating strength in various noncovalent interactions in hydrogen-, dihydrogen-, halogen-, tetrel-, pnicogen-, chalcogen-, and aerogen-bonded complexes and thereby to predict the interactive behavior of molecules. To sum up, MESP topology analysis has become one of the most effective modern techniques for understanding, interpreting, and predicting the intermolecular interactive behavior of molecules.