Binding of Solvent Molecules to a Protein Surface in Binary Mixtures Follows a Competitive Langmuir Model

Experiment and Simulation Study on the Adsorption Interaction between a Fluorescent Tracer and a Montmorillonite Crystal in Drilling Fluid

The adsorption interaction of oil field tracer in drilling fluid plays a significant role in tracer monitoring (TM) technology in the petroleum industry. In this work, the adsorption performances of Rhodamine B (RhB+) and fluorescein sodium (Fln-) tracers with montmorillonite (MMT) crystal in drilling fluid were investigated by both experimental and simulation methods. For the experimental aspect, the macroscopic results indicate thermodynamic monolayer adsorption by the Langmuir model and kinetic chemical adsorption by the pseudo-second-order (PSO) model. As a result, MMT shows a larger adsorption capacity (qm) for RhB+ than for Fln- with q m ( RhB + ) = 0.069 ⁡ g ⁡ g - 1 > q m ( Fln - ) = 0.016 g ⁡ g - 1 but stronger adsorption spontaneity (ΔrGmθ) for Fln- than for RhB+ with Δ r G m θ ( Fln - ) = - 7.92 kJ mol-1 < Δ r G m θ ( RhB + ) = - 6.90 kJ mol-1. Meanwhile, the interaction rate (k2) of Fln- was shown to be faster than that of RhB+ with k 2 ( Fln - ) = 1.07 ⁡ min - 1 ⁡ > k 2 ( RhB + ) = 0.95 ⁡ min - 1 ⁡ . For simulation insight, MMT shows much higher system stability (E) for Fln- than for RhB+ with E Fln - · · · MMT < E RhB + · · · MMT and Δ E Fln - · · · MMT > Δ E RhB + · · · MMT . Meanwhile, the microscopic simulation results reveal configuration changes and site distinctions for RhB+ and Fln- interactions with the MMT crystal. The different adsorption responses were explained by proposing an interaction mechanism of force dominance and position orientation. Specifically, Fln- was deduced to interact with metal (Al, Ca) and metalloid (Si) elements in the MMT crystal interlayer by "upright-insertion" orientation while RhB+ was deduced to interact with oxygen atoms on the MMT crystal surface by a "flat-lying" orientation. Hydrogen bonds, the electrostatic interaction, and the coordination effect were revealed to dominate for the interaction of tracer adsorption. This work provides both performance and mechanism investigation of fluorescent tracer adsorption interaction with the MMT crystal in drilling fluid, which is of great significance in reservoir exploitation.

Preclinical profiles of SKB264, a novel anti-TROP2 antibody conjugated to topoisomerase inhibitor, demonstrated promising antitumor efficacy compared to IMMU-132

Purpose

The aim of this study was to improve the intratumoral accumulation of an antibody-drug conjugate (ADC) and minimize its off-target toxicity, SKB264, a novel anti-trophoblast antigen 2 (TROP2) ADC that was developed using 2-methylsulfonyl pyrimidine as the linker to conjugate its payload (KL610023), a belotecan-derivative topoisomerase I inhibitor. The preclinical pharmacologic profiles of SKB264 were assessed in this study.

Methods

The in vitro and in vivo pharmacologic profiles of SKB264, including efficacy, pharmacokinetics-pharmacodynamics (PK-PD), safety, and tissue distribution, were investigated using TROP2-positive cell lines, cell-derived xenograft (CDX), patient-derived xenograft (PDX) models, and cynomolgus monkeys. Moreover, some profiles were compared with IMMU-132.

Results

In vitro, SKB264 and SKB264 monoclonal antibody (mAb) had similar internalization abilities and binding affinities to TROP2. After cellular internalization, KL610023 was released and inhibited tumor cell survival. In vivo, SKB264 significantly inhibited tumor growth in a dose-dependent manner in both CDX and PDX models. After SKB264 administration, the serum or plasma concentration/exposure of SKB264 (conjugated ADC, number of payload units ≥1), total antibody (Tab, unconjugated and conjugated mAb regardless of the number of the payload units), and KL610023 in cynomolgus monkeys increased proportionally with increasing dosage from 1 to 10 mg/kg. The linker stability of SKB264 was significantly enhanced as shown by prolonged payload half-life in vivo (SKB264 vs. IMMU-132, 56.3 h vs. 15.5 h). At the same dose, SKB264's exposure in tumor tissue was 4.6-fold higher than that of IMMU-132.

Conclusions

Compared with IMMU-132, the longer half-life of SKB264 had a stronger targeting effect and better antitumor activity, suggesting the better therapeutic potential of SKB264 for treating TROP2-positive tumors.

Association with Imidazole in the Cooperative Order-Disorder Transition in Aqueous Solution of Schizophyllan

Schizophyllan, a triple helical polysaccharide, exhibits cooperative order-disorder transition (CODT) in aqueous solutions. The transition transforms the ordered structure (triple helix I) formed between the branched side chains and solvent molecules into the disordered structure (triple helix II) without dissociation of the triple helix. The CODT behaviors in H₂O-imidazole mixtures containing HCl with different molar ratios of imidazole/HCl were investigated by adiabatic calorimetry and differential scanning calorimetry on two schizophyllan solutions with different molar masses. The transition temperature (T_r) and the transition enthalpy (ΔH_r) significantly depended on both of the mole fractions of imidazole and imidazole/HCl. The composition dependences of T_r and ΔH_r in H₂O-imidazole mixtures were analyzed with linear cooperative transition theory for the solvent-stabilizing effect in the mixture with active compounds. Theoretical analyses confirmed that both imidazole and imidazolium ions in the solutions competitively interact with the side chain of the triple helix.

Efficient Enzymatic Synthesis of Lipophilic Phenolic Glycoside Azelaic Acid Esters and Their Depigmenting Activity

In this paper, an enzymatic route for synthesizing phenolic glycoside azelaic acid esters was successfully set up via lipase-catalyzed esterification and transesterification. Among the lipases tested, Candida antarctica lipase B (Novozyme 435) showed the highest activity in catalyzing esterification and Thermomyces lanuginosus (Lipozyme TLIM) gave the highest substrate conversion in catalyzing transesterification for the synthesis of ester. The addition of 4A molecular sieves into the reaction system is found to be an effective method for in situ absorption of the byproduct water and methanol, with which the substrate conversions of the enzymatic esterification and transesterification were 98.7 and 95.1%, respectively. Also, the main product ratios in transesterification were above 99.0% with lipozyme TLIM as a catalyst because the hydrolysis reaction was hindered. The results of the physical and biological properties indicate that all esters had higher Clog p values than their parent compounds. Also, the esters showed higher intracellular tyrosinase inhibitory and depigmentating activities than phenolic glycosides, azelaic acid (AA), and their physical mixtures due to their higher membrane penetration and tyrosinase inhibitory effects. In particular, piceid 6″-O-azelaic acid ester (PIA) showed the strongest inhibitory effect against melanin production. Its inhibitory rate was 77.4% at a concentration of 0.25 mM, about 4.2 times higher than that of arbutin (18.5%).

Modelling of substrate access and substrate binding to cephalosporin acylases

Semisynthetic cephalosporins are widely used antibiotics currently produced by different chemical steps under harsh conditions, which results in a considerable amount of toxic waste. Biocatalytic synthesis by the cephalosporin acylase from Pseudomonas sp. strain N176 is a promising alternative. Despite intensive engineering of the enzyme, the catalytic activity is still too low for a commercially viable process. To identify the bottlenecks which limit the success of protein engineering efforts, a series of MD simulations was performed to study for two acylase variants (WT, M6) the access of the substrate cephalosporin C from the bulk to the active site and the stability of the enzyme-substrate complex. In both variants, cephalosporin C was binding to a non-productive substrate binding site (E86α, S369β, S460β) at the entrance to the binding pocket, preventing substrate access. A second non-productive binding site (G372β, W376β, L457β) was identified within the binding pocket, which competes with the active site for substrate binding. Noteworthy, substrate binding to the protein surface followed a Langmuir model resulting in binding constants K = 7.4 and 9.2 mM for WT and M6, respectively, which were similar to the experimentally determined Michaelis constants KM = 11.0 and 8.1 mM, respectively.

Cold-active extracellular lipase: Expression in Sf9 insect cells, purification, and catalysis

Cold-active lipases are gaining special attention nowadays as they are increasingly used in various industries such as fine chemical synthesis, food processing, and washer detergent. In the present study, an extracellular lipase gene from Yarrowia lipolytica (LIPY8) was cloned and expressed by baculovirus expression system. The recombinant lipase (LipY8p) was purified using chromatographic techniques, resulting in a purification factor of 25.7-fold with a specific activity of 1102.9U/mg toward olive oil. The apparent molecular mass of purified LipY8p was 40 kDa. The enzyme was most active at pH 7.5 and 17 °C. It exhibited maximum activity toward medium chain (C10) esters. The presence of transition metals such as Zn2+, Cu2+, and Ni2+ strongly inhibited the enzyme activity, which was enhanced by EDTA. The lipase activity was affected by detergents and was elevated by various organic solvents at 10% (v/v). These enzymatic properties make this lipase of considerable potential for biotechnological applications.

Simulation of protein diffusion: a sensitive probe of protein-solvent interactions

Aqueous solutions of Candida antarctica lipase B (CALB) were simulated considering three different water models (SPC/E, TIP3P, TIP4P) by a series of molecular dynamics (MD) simulations of three different box sizes (L = 9, 14, and 19 nm) to determine the diffusion coefficient, the water viscosity and the protein density. The protein-water systems were equilibrated for 500 ns, followed by 100 ns production runs which were analysed. The diffusional properties of CALB were characterized by the Stokes radius (R_S), which was derived from the diffusion coefficient and the viscosity. R_S was compared to the geometric radius (R_G) of CALB, which was derived from the protein density. R_S and R_G differed by 0.27 nm for SPC/E and by 0.40 and 0.39 nm for TIP3P and TIP4P, respectively, which characterizes the thickness of the diffusive hydration layer on the protein surface. The simulated hydration layer of CALB resulted in agreement with those experimentally determined for other seven different proteins of comparable size. By avoiding the most common pitfalls, protein diffusion can be reliably simulated: simulating different box sizes to account for the finite size effect, equilibrating the protein-water system sufficiently, and using the complete production run for the determination of the diffusion coefficient.

Enzymatic Production of Biodiesel: Strategies to Overcome Methanol Inactivation

Lipase-catalyzed transesterification of triglycerides and alcohols to obtain biodiesel is an environmentally friendly and sustainable route for fuels production since, besides proceeding in mild reaction conditions, it allows for the use of low-cost feedstocks that contain water and free fatty acids, for example non-edible oils and waste oils. This review article reports recent advances in the field and focus in particular on a major issue in the enzymatic process, the inactivation of most lipases caused by methanol, the preferred acyl acceptor used for alcoholysis. The recent results about immobilization of enzymes on nano-materials and the use of whole-cell biocatalysts, as well as the use of cell-surface display technologies and metabolic engineering strategies for microbial production of biodiesel are described. It is discussed also insight into the effects of methanol on lipases obtained by modeling approaches and report on studies aimed at mining novel alcohol stable enzymes or at improving robustness in existing ones by protein engineering.