Identification of a small molecule splicing inhibitor targeting UHM domains.

Splicing factor mutations are frequent in myeloid neoplasms, blood cancers, and solid tumors. Cancer cells harboring these mutations present a particular vulnerability to drugs that target splicing factors such as SF3b155 or CAPERα. Still, the arsenal of chemical probes that target the spliceosome is very limited. U2AF homology motifs (UHMs) are common protein interaction domains among splicing factors. They present a hydrophobic pocket ideally suited to anchor small molecules with the aim to inhibit protein-protein interaction. Here, we combined a virtual screening of a small molecules database and an in vitro competition assay and identified a small molecule, we named UHMCP1 that prevents the SF3b155/U2AF65 interaction. NMR analyses and molecular dynamics simulations confirmed the binding of this molecule in the hydrophobic pocket of the U2AF65 UHM domain. We further provide evidence that UHMCP1 impacts RNA splicing and cell viability and is therefore an interesting novel compound targeting an UHM domain with potential anticancer properties.

Development of polymer-based nanoparticles for zileuton delivery to the lung: PMeOx and PMeOzi surface chemistry reduces interactions with mucins.

In this paper, two amphiphilic graft copolymers were synthesized by grafting polylactic acid (PLA) as hydrophobic chain and poly(2-methyl-2-oxazoline) (PMeOx) or poly(2-methyl-2-oxazine) (PMeOzi) as hydrophilic chain, respectively, to a backbone of α,ß-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA). These original graft copolymers were used to prepare nanoparticles delivering Zileuton in inhalation therapy. Among various tested methods, direct nanoprecipitation proved to be the best technique to prepare nanoparticles with the smallest dimensions, the narrowest dimensional distribution and a spherical shape. To overcome the size limitations for administration by inhalation, the nano-into-micro strategy was applied, encapsulating the nanoparticles in water-soluble mannitol-based microparticles by spray-drying. This process has allowed to produce spherical microparticles with the proper size for optimal lung deposition, and, once in contact with fluids mimicking the lung district, able to dissolve and release non-aggregated nanoparticles, potentially able to spread through the mucus, releasing about 70% of the drug payload in 24 h.

Paclitaxel-Loaded Magnetic Nanoparticles Based on Biotinylated N-Palmitoyl Chitosan: Synthesis, Characterization and Preliminary In Vitro Studies.

A considerable interest in cancer research is represented by the development of magnetic nanoparticles based on biofunctionalized polymers for controlled-release systems of hydrophobic chemotherapeutic drugs targeted only to the tumor sites, without affecting normal cells. The objective of the paper is to present the synthesis and in vitro evaluation of the nanocomposites that include a magnetic core able to direct the systems to the target, a polymeric surface shell that provides stabilization and multi-functionality, a chemotherapeutic agent, Paclitaxel (PTX), and a biotin tumor recognition layer. To our best knowledge, there are no studies concerning development of magnetic nanoparticles obtained by partial oxidation, based on biotinylated N-palmitoyl chitosan loaded with PTX. The structure, external morphology, size distribution, colloidal and magnetic properties analyses confirmed the formation of well-defined crystalline magnetite conjugates, with broad distribution, relatively high saturation magnetization and irregular shape. Even if the ability of the nanoparticles to release the drug in 72 h was demonstrated, further complex in vitro and in vivo studies will be performed in order to validate the magnetic nanoparticles as PTX delivery system.

Hydrophobic and polar interactions of FDA-approved small molecule protein kinase inhibitors with their target enzymes.

Dysregulation and mutations of protein kinases play causal roles in many diseases including cancer. The KLIFS (kinase-ligand interaction fingerprint and structure) catalog includes 85 ligand binding-site residues occurring in both the small and large protein kinase lobes. Except for allosteric inhibitors, all FDA-approved drug-target enzyme complexes display hydrophobic interactions involving catalytic spine residue-6 (KLIFS-77), catalytic spine residue-7 (KLIFS-11), and catalytic spine residue-8 (KLIFS-15) within the small lobe and residues within the hinge-linker region (KLIFS-46-52). Except for allosteric antagonists, the approved drugs form hydrogen bonds with the third hinge residue (KLIFS-48) of their target. Most of the approved drugs, including the allosteric inhibitors, interact with the small lobe gatekeeper residue (KLIFS-45). The type IIA inhibitors have the most hydrophobic interactions with their target enzymes. These include interactions with KLIFS-27/31/35/61/66 residues of the back pocket within both the small and large lobes. There is also interaction with KLIFS-68 (regulatory spine residue-1), the conserved histidine of the catalytic loop that is found in the back pocket of type II antagonists, but within the front pocket of the other types of inhibitors. Owing to the participation of protein kinase signaling cascades in a wide variety of physiological and pathological processes, one can foresee the increasing use of targeted inhibitors both as primary and secondary treatments for many illnesses. Further studies of protein kinase signal transduction pathways promise to yield new and actionable information that will serve as a basis for fundamental and applied biomedical breakthroughs.

Effect of Polymer Species on Maximum Aqueous Phase Supersaturation Revealed by Quantitative Nuclear Magnetic Resonance Spectroscopy.

The polymer used in an amorphous solid dispersion (ASD) formulation impacts the maximum achievable drug supersaturation. Herein, the effect of dissolved polymer on drug concentration in the aqueous phase when a drug-rich phase was generated by liquid-liquid phase separation (LLPS) was investigated for different polymers at various concentrations of drug and polymer. Solution nuclear magnetic resonance (NMR) spectroscopy revealed that polyvinylpyrrolidone (PVP), polyvinylpyrrolidone/vinyl acetate (PVP-VA), and hypromellose (HPMC) distributed into the ibuprofen (IBP)-rich phase formed by LLPS when the amorphous solubility of IBP was exceeded. The amount of polymer in the drug-rich phase increased for higher-molecular-weight grades of PVP and HPMC. Moreover, PVP-VA showed a greater extent of distribution into the IBP-rich phase compared to PVP, and this is attributed to its reduced hydrophilicity resulting from the incorporation of vinyl acetate monomers. Direct quantification by NMR measurements indicated that the IBP concentration in the aqueous phase decreased as the amount of polymer in the IBP-rich phase increased. This can be attributed to a reduction of the chemical potential of IBP in the IBP-rich phase. The reduction in dissolved IBP concentration was greater for the IBP/PVP-VA system compared to the IBP/HPMC system, as a result of more extensive drug-polymer interactions in the former system. The present study highlights the impact of polymer selection on the attainable supersaturation of the drug and the factors that need to be considered in the formulation of ASDs to obtain optimized in vivo performance.

Design of Functional Nanoparticles for Intractable Disease Therapy.

Protein affinity reagents are widely used for basic research, diagnostics, and disease therapy. Antibodies and their fragments are known as the most common protein affinity reagents. They specifically and strongly bind to target molecules and inhibit their functions. Thus, antibody drugs have increased in the recent two decades for disease therapy, such as cancer. These strong protein-protein interactions are composed of a nexus of multiple weak interactions. Synthetic polymers that bind to target molecules have been developed by the imitation of protein-protein interactions. These polymers show nanomolar affinity for the target and neutralize their functions; thus, they are of significant interest as a cost-effective protein affinity reagent. We have been developing synthetic polymer nanoparticles (NPs) that bind to target peptides and proteins by the inclusion of several functional monomers, such as charged and hydrophobic monomers. In this review, the focus is on the design of synthetic polymer NPs that bind to target molecules for disease therapy. We succeeded in neutralization of toxic peptides and signaling proteins both in vitro and in vivo. Additionally, linear polymers were modified on a lipid nanoparticle surface to improve polymer biodistribution. Our recent findings should provide useful information for the development of abiotic protein affinity reagents.

Impact of Drug Conjugation and Loading on Target Antigen Binding and Cytotoxicity in Cysteine Antibody-Drug Conjugates.

Antibody-drug conjugates (ADCs) consist of a target-specific antibody that is covalently conjugated to a drug via a linker. ADCs are designed to deliver cytotoxic drugs (payloads), specifically to cancer cells, while minimizing systemic toxicity. Conventional cysteine conjugation typically results in the formation of ADC molecules containing a heterogeneous mixture of 2, 4, 6, and 8 drug-loaded species. The drug-to-antibody ratio (DAR) of the mixture represents the weighted average of these species. In this report, we have investigated the impact of the hydrophobicity of payloads and the overall drug loading on the in vitro binding and cytotoxicity of ADC species. Several ADCs were prepared by conventional cysteine conjugation using different payloads. ADC species with different DAR values were purified from the ADC mixture and characterized by standard analytical techniques. These ADC species were evaluated for target antigen binding using an immunoassay, enzyme-linked immunosorbent assay (ELISA). The potency was assessed using a cell-based cytotoxicity assay. These structure-function studies lead to a better understanding of factors that impact the in vitro target binding and cytotoxicity of ADC species. ADC species containing hydrophobic payloads with high DAR were found to have lower target binding by ELISA compared to that of the unconjugated antibody or the heterogeneous reference ADC with DAR ∼4. Under similar assay conditions, the ADCs conjugated to hydrophilic payloads did not show a significant impact on the target binding. The cytotoxic potency of ADC species increased with increasing level of drug loading in the cell-based cytotoxicity assay.

Heparin Enriched-WPI Coating on Ti6Al4V Increases Hydrophilicity and Improves Proliferation and Differentiation of Human Bone Marrow Stromal Cells.

Titanium alloy (Ti6Al4V) is one of the most prominent biomaterials for bone contact because of its ability to bear mechanical loading and resist corrosion. The success of Ti6Al4V implants depends on bone formation on the implant surface. Hence, implant coatings which promote adhesion, proliferation and differentiation of bone-forming cells are desirable. One coating strategy is by adsorption of biomacromolecules. In this study, Ti6Al4V substrates produced by additive manufacturing (AM) were coated with whey protein isolate (WPI) fibrils, obtained at pH 2, and heparin or tinzaparin (a low molecular weight heparin LMWH) in order to improve the proliferation and differentiation of bone-forming cells. WPI fibrils proved to be an excellent support for the growth of human bone marrow stromal cells (hBMSC). Indeed, WPI fibrils were resistant to sterilization and were stable during storage. This WPI-heparin-enriched coating, especially the LMWH, enhanced the differentiation of hBMSC by increasing tissue non-specific alkaline phosphatase (TNAP) activity. Finally, the coating increased the hydrophilicity of the material. The results confirmed that WPI fibrils are an excellent biomaterial which can be used for biomedical coatings, as they are easily modifiable and resistant to heat treatments. Indeed, the already known positive effect on osteogenic integration of WPI-only coated substrates has been further enhanced by a simple adsorption procedure.

ßB2 W151R mutant is prone to degradation, aggregation and exposes the hydrophobic side chains in the fourth Greek Key motif.

Studies have established that congenital cataract is the major cause of blindness in children across the globe. The ß-crystallin protein family is the richest and most soluble structural protein in the lens. Their solubility and stability are essential in maintaining lens transparency. In this study, we identified a novel ßB2 mutation W151R in a rare progressive cortical congenital cataract family and explored its pathogenesis using purified protein and mutant related cataract-cell models. Due to its low solubility and poor structural stability, the ßB2 W151R mutation was prone to aggregation. Moreover, the W151R mutation enhanced the exposure of the hydrophobic side chains in the fourth Greek Key motif, which were readily degraded by trypsin. However, upon the administration of lanosterol, the negative effect of the W151R mutation was reversed. Therefore, lanosterol is a potential therapeutic option for cataracts.

Design, synthesis and bioevaluation of inhibitors targeting HSP90-CDC37 protein-protein interaction based on a hydrophobic core.

HSP90-CDC37 protein-protein interaction (PPI) works as a kinase specific-molecular chaperone system to regulate the maturation of kinases. Currently, selectively disrupting HSP90-CDC37 PPI, rather than the direct inhibition of the ATPase function of HSP90, is emerging as a promising strategy for cancer therapy by specifically blocking the maturation of kinases. However, due to the limited understanding of HSP90-CDC37 binding interface, design of small molecule inhibitors targeting HSP90-CDC37 PPI is challenging. In this work, based on the binding mode of compound 11 (previously reported by our group), we discovered a hydrophobic pocket centered on Phe213, which was previously unknown, contributing to the binding affinity of HSP90-CDC37 PPI inhibitors. A series of hydrophobic substituted inhibitors were utilized to confirm the importance of Phe213 hydrophobic core. Finally, we obtained an optimum compound DDO-5994 (exhibited an ideal binding pattern on hydrophobic core) with improved binding affinity (KD = 5.52 µM) and antiproliferative activity (IC50 = 6.34 µM). Both in vitro and in vivo assays confirmed DDO-5994 as a promising inhibitor to exhibit ideal antitumor efficacy through blocking HSP90-CDC37 PPI.

In Silico Drug-designing Studies on Sulforaphane Analogues: Pharmacophore Mapping, Molecular Docking and QSAR Modeling.

AIMS: In the presented work we successfully discovered several novel NQO1 inducers using the computational approaches. BACKGROUND: The phytochemical sulforaphane (SFN) is a potent inducer of carcinogen detoxication enzymes like NAD(P)H:quinone oxidoreductase 1 (NQO1) through the Kelch-like erythroid cellderived protein with CNC homology[ECH]-associated protein 1 (Keap1)-[NF-E2]-related factor 2 (Nrf2) signaling pathway. OBJECTIVE: In this paper, we report the first QSAR and pharmacophore modeling study of sulforaphane analogues as NQO1 inducers. The pharmacophore model and understanding the relationships between the structures and activities of the known inducers will give useful information on the structural basis for NQO1 enzymatic activity and lead optimization for future rational design of new sulforaphane analogues as potent NQO1 inducers. METHODS: In this study, a combination of QSAR modeling, pharmacophore generation, virtual screening and molecular docking was performed on a series of sulforaphane analogues as NQO1 inducers. RESULTS: In deriving the QSAR model, the stepwise multiple linear regression established a reliable model with the training set (N: 43, R: 0.971, RMSE: 0.216) and test set (N: 14, R: 0.870, RMSE: 0.324, Q2: 0.80) molecules. The best ligand-based pharmacophore model comprised two hydrophobic (HY), one ring aromatic (RA) and three hydrogen bond acceptor (HBA) sites. The model was validated by a testing set and the decoys set, Güner-Henry (GH) scoring methods, etc. The enrichment of model was assessed by the sensitivity (0.92) and specificity (0.95). Moreover, the values of enrichment factor (EF) and the area under the receiver operating characteristics curve (AUC) were 12 and 0.94, respectively. This well-validated model was applied to screen two Asinex libraries for the novel NQO1 inducers. The hits were subsequently subjected to molecular docking after being filtering by Lipinski's, MDDR-like, and Veber rules as well as evaluating their interaction with three major drugmetabolizing P450 enzymes, CYP2C9, CYP2D6 and CYP3A4. Ultimately, 12 hits filtered by molecular docking were subjected to validated QSAR model for calculating their inducer potencies and were introduced as potential NQO1 inducers for further investing action. CONCLUSION: Conclusively, the validated QSAR model was applied on the hits to calculate their inducer potencies and these 12 hits were introduced as potential NQO1 inducers for further investigations.

Preparation and application of a polymer with pH/temperature-responsive targeting.

Targeted drug carrier systems not only prolong the long-term circulation of drugs, but also improve their bioavailability. To obtain a pH/temperature synergistically responsive polymer carrier, temperature and pH-sensitive groups were chemically grafted onto a cassava starch backbone. Secondly, the structure of the polymer micelle carrier was characterized, and finally the drug loading performance and capacity of the drug carrier were explored. It was observed that cumulative drug release was low when the temperature and pH values met one of two conditions. Only at a high temperature and low pH (T = 38 °C, pH = 5.5, as in tumor tissue) did cumulative drug release reach its maximum value. The design of the polymer carrier described in the present study represents a novel paradigm in precision release drug carriers.

Understanding the Factors Influencing Chitosan-Based Nanoparticles-Protein Corona Interaction and Drug Delivery Applications.

Chitosan is a polymer that is extensively used to prepare nanoparticles (NPs) with tailored properties for applications in many fields of human activities. Among them, targeted drug delivery, especially when cancer therapy is the main interest, is a major application of chitosan-based NPs. Due to its positive charges, chitosan is used to produce the core of the NPs or to cover NPs made from other types of polymers, both strategies aiming to protect the carried drug until NPs reach the target sites and to facilitate the uptake and drug delivery into these cells. A major challenge in the design of these chitosan-based NPs is the formation of a protein corona (PC) upon contact with biological fluids. The composition of the PC can, to some extent, be modulated depending on the size, shape, electrical charge and hydrophobic / hydrophilic characteristics of the NPs. According to the composition of the biological fluids that have to be crossed during the journey of the drug-loaded NPs towards the target cells, the surface of these particles can be changed by covering their core with various types of polymers or with functionalized polymers carrying some special molecules, that will preferentially adsorb some proteins in their PC. The PC's composition may change by continuous processes of adsorption and desorption, depending on the affinity of these proteins for the chemical structure of the surface of NPs. Beside these, in designing the targeted drug delivery NPs one can take into account their toxicity, initiation of an immune response, participation (enhancement or inhibition) in certain metabolic pathways or chemical processes like reactive oxygen species, type of endocytosis of target cells, and many others. There are cases in which these processes seem to require antagonistic properties of nanoparticles. Products that show good behavior in cell cultures may lead to poor in vivo results, when the composition of the formed PC is totally different. This paper reviews the physico-chemical properties, cellular uptake and drug delivery applications of chitosan-based nanoparticles, specifying the factors that contribute to the success of the targeted drug delivery. Furthermore, we highlight the role of the protein corona formed around the NP in its intercellular fate.

Antioxidant and antibacterial activities, interfacial and emulsifying properties of the apo and holo forms of purified camel and bovine α-lactalbumin.

The antioxidant and antibacterial activities of camel and bovine α-lactalbumin (α-La) in both calcium-loaded (holo) and calcium-depleted (apo) forms were investigated and compared. Antioxidant assay showed that camel and bovine α-La exhibited significant Ferric-reducing antioxidant power (FRAP), ferrous iron-chelating activity (FCA) and antiradical activities especially in their apo form. Camel apo α-La also exhibited attractive antibacterial activities against Gram-negative bacteria (Pseudomonas aeruginosa) and against fungal pathogens species (Penicillium bilaiae, Aspergillus tamari and Aspergillus sclerotiorum). Likewise, emulsifying properties (emulsification ability (EAI) and stability (ESI) indexes) and the surface characteristics (surface hydrophobicity, ζ-potential and interfacial tension) of the α-La were assessed. Maximum EAI were found at pH 7.0, with higher EAI values for the camel apo α-La (EAI ~19.5 m2/g). This behavior was explained by its relative high surface hydrophobicity and its greater efficiency to reduce the surface tension at the oil-water interface. Furthermore, emulsions were found to be more stable at pH 7.0 compared to pH 5.0 (ESI ~50%) due to the higher electrostatic repulsive forces between oil droplets at pH 7.0 in consistence with the ζ-potential results. This study concluded that the camel apo α-La has antibacterial, antioxidant, and emulsifying properties in agricultural and food industries.

Tissue-sealing and anti-adhesion properties of an in situ hydrogel of hydrophobically-modified Alaska pollock-derived gelatin.

Anastomotic leakage and tissue adhesion are significant complications associated with colorectal surgeries, such as the resection of colorectal cancer. However, an effective biomedical apparatus has yet to be developed to address both complications. In the present study, we developed a tissue-sealing, anti-adhesive hydrogel composed of decyl group-modified gelatin (C10-ApGltn) and a poly (ethylene glycol)-based crosslinker. C10-ApGltn based hydrogel (C10-gel) demonstrated increased elastic modulus and suppressed swelling ratio compared with the unmodified ApGltn. Furthermore, C10-gel effectively sealed a water leakage model of intestine tissue and prevented contact between two intestinal tissue samples. In vivo experiments revealed that C10-gel degraded almost entirely in 28 days and prevented cell infiltration for 14 days, which effectively inhibits tissue adhesion. Therefore, C10-gel is a biocompatible hydrogel that can be used to mitigate or prevent anastomotic leakage and prevent tissue adhesion in colorectal surgery.

Comparison of Chemotherapeutic Activities of Rhodamine-Based GUMBOS and NanoGUMBOS.

Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties that result from their lipophilic cationic structures. In previous research, we have found that conversion of Rhodamine 6G into nanoGUMBOS, i.e., nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS), led to selective chemotherapeutic toxicity for cancer cells over normal cells. Herein, we investigate the chemotherapeutic activity of GUMBOS derived from four different rhodamine derivatives, two bearing an ester group, i.e., Rhodamine 123 (R123) and SNAFR-5, and two bearing a carboxylic acid group, i.e., rhodamine 110 (R110) and rhodamine B (RB). In this study, we evaluate (1) relative hydrophobicity via octanol-water partition coefficients, (2) cytotoxicity, and (3) cellular uptake in order to evaluate possible structure-activity relationships between these different compounds. Intriguingly, we found that while GUMBOS derived from R123 and SNAFR-5 formed nanoGUMBOS in aqueous medium, no distinct nanoparticles are observed for RB and R110 GUMBOS. Further investigation revealed that the relatively high water solubility of R110 and RB GUMBOS hinders nanoparticle formation. Subsequently, while R123 and SNAFR-5 displayed selective chemotherapeutic toxicity similar to that of previously investigated R6G nanoGUMBOS, the R110 and RB GUMBOS were lacking in this property. Additionally, the chemotherapeutic toxicities of R123 and SNAFR-5 nanoGUMBOS were also significantly greater than R110 and RB GUMBOS. Observed results were consistent with decreased cellular uptake of R110 and RB as compared to R123 and SNAFR-5 compounds. Moreover, these results are also consistent with previous observations that suggest that nanoparticle formation is critical to the observed selective chemotherapeutic properties as well as the chemotherapeutic efficacy of rhodamine nanoGUMBOS.

Cyclodextrin binding constants as a function of pH for compounds with multiple pKa values.

Complex formation between cyclodextrins and ionizable guest molecules depends on pH. In general, the neutral species of an ionizable guest molecule has the highest affinity for the cyclodextrin cavity, but ionized species will also be able to form complexes with cyclodextrins. This work presents a theoretical expression for the relationship between the stability constant and pH for interaction between neutral cyclodextrins and ionizable guest molecules with multiple pKa values. Input parameters for the theoretical expression are pKa values of the guest molecule and stability constants for the complex at specific pH values. The pH profile of the stability constant for a complex depends on the acid-base properties of the guest and the closeness of the pKa values, and examples of pH profiles for polyprotic acids, bases and amphoteric guests are shown. Empirical data sets from the literature were used to confirm the accuracy of the theoretical expression, and Monte Carlo simulations were used to validate that the theoretical expression yield a good fit to empirical data. Lastly, an experimental protocol was suggested, and a freely available graphical user interface was presented to facilitate easy use of the theoretical expression.

The Lysosomotropic Activity of Hydrophobic Weak Base Drugs is Mediated via Their Intercalation into the Lysosomal Membrane.

Lipophilic weak base therapeutic agents, termed lysosomotropic drugs (LDs), undergo marked sequestration and concentration within lysosomes, hence altering lysosomal functions. This lysosomal drug entrapment has been described as luminal drug compartmentalization. Consistent with our recent finding that LDs inflict a pH-dependent membrane fluidization, we herein demonstrate that LDs undergo intercalation and concentration within lysosomal membranes. The latter was revealed experimentally and computationally by (a) confocal microscopy of fluorescent compounds and drugs within lysosomal membranes, and (b) molecular dynamics modeling of the pH-dependent membrane insertion and accumulation of an assortment of LDs, including anticancer drugs. Based on the multiple functions of the lysosome as a central nutrient sensory hub and a degradation center, we discuss the molecular mechanisms underlying the alteration of morphology and impairment of lysosomal functions as consequences of LDs' intercalation into lysosomes. Our findings bear important implications for drug design, drug induced lysosomal damage, diseases and pertaining therapeutics.

Fast chemical force microscopy demonstrates that glycopeptidolipids define nanodomains of varying hydrophobicity on mycobacteria.

Mycobacterium abscessus is an emerging multidrug-resistant bacterial pathogen causing severe lung infections in cystic fibrosis patients. A remarkable trait of this mycobacterial species is its ability to form morphologically smooth (S) and rough (R) colonies. The S-to-R transition is caused by the loss of glycopeptidolipids (GPLs) in the outer layer of the cell envelope and correlates with an increase in cording and virulence. Despite the physiological and medical importance of this morphological transition, whether it involves changes in cell surface properties remains unknown. Herein, we combine recently developed quantitative imaging (QI) atomic force microscopy (AFM) with hydrophobic tips to quantitatively map the surface structure and hydrophobicity of M. abscessus at high spatiotemporal resolution, and to assess how these properties are modulated by the S-to-R transition and by treatment with an inhibitor of the mycolic acid transporter MmpL3. We discover that loss of GPLs leads to major modifications in surface hydrophobicity, without any apparent change in cell surface ultrastructure. While R bacilli are homogeneously hydrophobic, S bacilli feature unusual variations of nanoscale hydrophobic properties. These previously undescribed cell surface nanodomains are likely to play critical roles in bacterial adhesion, aggregation, phenotypic heterogeneity and transmission, and in turn in virulence and pathogenicity. Our study also suggests that MmpL3 inhibitors show promise in nanomedicine as chemotherapeutic agents to interfere with the highly hydrophobic nature of the mycobacterial cell wall. The advantages of QI-AFM with hydrophobic tips are the ability to map chemical and structural properties simultaneously and at high resolution, applicable to a wide range of biosystems.

Insight into the binding behavior of ceritinib on human α-1 acid glycoprotein: Multi-spectroscopic and molecular modeling approaches.

Ceritinib is a second-generation anaplastic lymphoma kinase (ALK) inhibitor for mainly treating non-small cell lung cancer (NSCLC). This investigation focused on to clarify in detail the binding behavior between human α-1 acid glycoprotein (HAG) and ceritinib by means of multi-spectroscopic and molecular modeling approaches. Fluorescence data obtained at four different temperatures indicated ceritinib quenched the endogenous fluorescence of HAG by a static quenching mechanism. Based on the Kb value at 105 M-1 level, it can be inferred that the binding affinity between both is strong. From findings of thermodynamic parameter analysis, the competitive experiments with ANS and sucrose as well as molecular dynamic (MD) simulation, it can be inferred that hydrophobicity, hydrogen bonding, van der Waals forces as well as electrostatic interactions exist in the binding interaction between ceritinib and HAG. The findings from UV absorption, circular dichroism, and synchronous fluorescence spectroscopy indicated that the change in the microenvironment around the protein structure, secondary structure and tryptophan residues occurred after interaction with ceritinib. The data from FRET analysis confirmed that the non-radiative energy transfer between the two existed and the binding distance between the acceptor (ceritinib) and donor (HAG) was 2.11 nm. Meantime, the influence of Ca2+, Cu2+, Ni2+, Co2+, and Zn2+ ions on the binding interaction of ceritinib with HAG were obvious, especially Zn2+ ion.