Formation Of Binary Complexes Research Articles

Interplay between soluble and insoluble protein/calcium/phytic acid complexes in dispersions of faba bean and pea protein concentrates around neutral pH

Pulses are rich in proteins and a good source of calcium. However, antinutritional compounds such as phytic acid can bind to proteins and minerals to form complexes, reducing their digestibility and bioavailability, respectively. This study investigated interactions and potential complex formation between phytic acid, calcium, and proteins in pea and faba bean concentrate dispersions. The solubility of the 3 compounds was measured at pH 6.5, 7.0 and 7.5. Formation of complexes was investigated by chelating calcium upon EDTA addition or by removing proteins via ultrafiltration. Protein profiles were compared using Size Exclusion Chromatography (SEC). For both pea and faba bean, protein solubility increased with increasing pH. Phytic acid solubility was minimum at pH 7.0, while simultaneously calcium solubility was maximum. Protein solubility increased with EDTA addition compared to the control at pH 6.5 (pea and faba bean) and 7.0 (pea), supporting the presence of insoluble binary complexes between calcium and proteins. The concomitant rise in phytic acid solubility for pea (pH 6.5 and 7.0) highlighted the formation of either insoluble binary (phytic acid to calcium) or ternary complexes. Also, the formation of soluble protein complexes with phytic acid and, possibly, with calcium was highlighted. Small amounts of soluble ternary complexes were observed at pH 7.5. SEC results showed an increase in globulin's (especially legumin) solubility after calcium chelation; this demonstrated the formation of insoluble complexes mediated by calcium. This study highlighted that the different protein fractions from pulses must be considered separately in their ability to establish complexes with calcium and phytic acid.

Preparation of a Pt(II)-3-Hydroxy-2-tolyl-4H-chromen-4-one Complex Having Antimicrobial, Anticancerous, and Radical Scavenging Activities with Related Computational Studies.

A novel benzopyran-based platinum (II)-3-hydroxy-2-tolyl-4H-chromen-4-one (HToC) complex has been prepared and studied by UV-visible spectrophotometry. The study is based on the colored complexation between Pt(II) and HToC in the pH range of 8.92-9.21, resulting in the formation of a stable binary yellow complex exhibiting λmax at 509-525 nm. The formed complex maintains linearity between 0.0 and 1.8 μg Pt(II) mL-1. The well-known qualitative analytical methods, including Job's method of continuous variations and the mole ratio approach, have both proven that the stoichiometry of the complex is 1:2 [Pt(II)/HToC]. Hence, the analytical results suggest that the formed platinum complex exhibits a square planar geometry. The values of various attributes corresponding to spectrophotometric studies and statistical calculations, such as the molar extinction coefficient (6.790 × 104 L mol-1 cm-1), Sandell's sensitivity (0.0029 μg Pt(II) cm-2), standard deviation (± 0.0011), RSD (0.317%), limit of detection (0.0147 μg mL-1) and correlation coefficient (0.9999), show that the performed study satisfies all of the criteria for good sensitivity, versatility, and cost-effectiveness. In order to have an apprehension of the molecular geometry and other structural specifics of the complex, DFT studies have been carried out. The in vitro anticancer potential of the ligand and its platinum complex in the human breast cancer cell line (T-27D), as determined by the MTT assay, reveals that the complex has better antiproliferative potential than the ligand. The antimicrobial potential of the complex has been successfully tested against both Gram-positive and -negative bacteria. Antioxidant capacity results suggest the better radical scavenging capacity of the complex than that of the ligand.

Implicatons of Metal Complexes in Biology and Medicine the System Cadmium (II)/ Iron (II)/ Zinc (II)-Hydroxyproline

The importance of metal ions to essential functions of living systems and for the well being of living organisms is known. Metal ions are fundamental elements for the maintenance of the life spans of the human, animals and plants. The stability constants of Cd2+, Fe2+ and Zn2+ complexes with hydroxyproline were determined by Paper Electrophoretic Technique (PET). This method is based on the movement of a spot of metal ion in an electric field at various pH of background electrolyte. A graph of pH against mobility gives information about the formation of binary complexes and permit to calculate their stability constants. The stability constant of the ML and ML2 complexes of Cd (II) – hydroxyproline, Fe (II) – hydroxyproline and Zn (II) – hydroxyproline, have been found to be (4.41 ± 0.01; 2.95 ± 0.06) (4.11 ± 0.01; 2.81 ± 0.11 and (4.83 ± 0.02; 3.28 ± 0.07) ( logarithm stability constant values), respectively at ionic strength 0.1 mole L-1 (per chloric acid as background electrolyte) and a temperature of 35 0C, The first and second stability constants of metal complexes follow the order Zn (II) > Cd (II) > Fe (II). Metal complexes can offer their action such as anti-inflammatory, antibiotic, anti-thyroid and anticancer compounds. Metal based drugs bioactivity can be increased by metal chelation, which in turn increase their absorbance and stability. Recent advances in inorganic chemistry have made possible formation of a number of metal complexes with organic ligands of interest which can be use as therapeutic agents.

Storage stability and multi-spectroscopy analysis of the ternary complex induced by mulberry anthocyanin extract interacting with whey protein isolate and rutin under acidic conditions

In the present study, we have investigated the relevant mechanisms underlying the stabilizing effects of whey protein isolate (WPI) and rutin (Ru) on the mulberry anthocyanin extract (MAE) solution at pH 3.6 during storage. The results demonstrated that there was no pronounced difference in color between the MAE solutions when adding WPI and Ru separately and together. However, the combined use of WPI and Ru reduced the total anthocyanin degradation rate by 16.2% and 18.3% compared to WPI and Ru used individually, respectively, after 9 days of storage at 40 °C. Fluorescence, UV–visible, Fourier transform infrared, and circular dichroism spectroscopies, as well as particle size and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, indicated that the formation of binary and ternary complexes involving β-lactoglobulin (β-LG), cyanidin-3-O-glucoside (C3G), and Ru. The primary interaction between β-LG and C3G was electrostatic interaction, with an enthalpy change (ΔH) of −25.02 kJ mol−1 and an entropy change (ΔS) of 7.89 J mol−1 K−1 at 298 K, whereas the interactions between β-LG and Ru involved hydrogen bonding and van der Waals force, with ΔH of −124.80 kJ mol−1 and ΔS of −291.72 J mol−1 K−1 at 298 K. Furthermore, a looser, more open, and disordered structure and larger particle size were observed in protein after the addition of C3G/Ru. The presence of Ru in the ternary complex favored the development of these characteristics. Overall, to protect anthocyanins, β-LG and Ru could exert complexation and copigmentation effects on C3G, respectively. The findings of this study provide a foundation for employing ternary complexes to increase the storage stability of anthocyanins.

Binary and ternary complexes of epinephrine with alginate and biologically and environmentally relevant metal cations.

The speciation of epinephrine (Eph -) in the presence of alginate (Alg 2-) and two biological and environmental relevant metal cations (Cu2+, UO2 2+) was investigated at T = 298.15K, I = 0.15-1.00moldm-3 in NaCl(aq). The formation of binary and ternary complexes was evaluated and, since epinephrine can behave as a zwitterion, the Eph -/Alg 2- interaction was studied by means of DOSY NMR. The dependence of the equilibrium constants on ionic strength was studied using an extended Debye-Hückel type equation and the SIT approach. The effect of temperature was investigated by means of isoperibolic titration calorimetry: the entropic contribution was the driving force for the Cu2+/Eph - complexes formation. The sequestering ability of Eph - and Alg 2- on Cu2+, evaluated by the pL0.5 calculation, increased with pH and ionic strength. The determination of pM parameter showed that Eph - had a higher Cu2+ affinity with respect to Alg 2-. The formation of Eph -/Alg 2- species was also investigated by UV-Vis spectrophotometry and 1H NMR measurements. The ternary Cu2+/Eph -/Alg 2- and Cu2+/UO2 2+/Eph - interactions were also studied. The "extra-stability" calculated for the mixed ternary species confirmed that their formation was thermodynamically favorable.

Molecular recognition of tripeptides containing tryptophan by cucurbit[8]uril: A computational study

In this work, molecular dynamics (MD) simulations and time-dependent density functional theory (TD-DFT) calculations were applied to study the formation of binary and ternary complexes between cucurbit[8]uril (CB8) and three tryptophan-containing tripeptides (WGG, GWG, and GGW), as well as heteroternary complexes of the tripeptides in the presence of methyl viologen (MV) as an auxiliary ligand. All complexes were stable in water, and exhibited encapsulation of the indole moiety of W. Analysis of the MD trajectories of the homoternary complexes revealed π-π stacking within the CB8 cavity between the indole rings. MM-PBSA analysis indicated higher binding energy for tripeptides containing W residue at the N-terminus. The heteroternary complexes showed two binding modes, one with MV fully included (and π-π stacked with the indole ring) and the other with MV mostly excluded. The computed UV–Visible spectra of the free guests and their heteroternary complexes exhibited new bands emerged in the spectra of the complexes, which resulted from the transitions from HOMO and HOMO–1 to LUMO related to W–MV charge transfer (CT) complexes.

Regulation of cargo exocytosis by a Reps1-Ralbp1-RalA module.

Surface levels of membrane proteins are determined by a dynamic balance between exocytosis-mediated surface delivery and endocytosis-dependent retrieval from the cell surface. Imbalances in surface protein levels perturb surface protein homeostasis and cause major forms of human disease such as type 2 diabetes and neurological disorders. Here, we found a Reps1-Ralbp1-RalA module in the exocytic pathway broadly regulating surface protein levels. Reps1 and Ralbp1 form a binary complex that recognizes RalA, a vesicle-bound small guanosine triphosphatases (GTPase) promoting exocytosis through interacting with the exocyst complex. RalA binding results in Reps1 release and formation of a Ralbp1-RalA binary complex. Ralbp1 selectively recognizes GTP-bound RalA but is not a RalA effector. Instead, Ralbp1 binding maintains RalA in an active GTP-bound state. These studies uncovered a segment in the exocytic pathway and, more broadly, revealed a previously unrecognized regulatory mechanism for small GTPases, GTP state stabilization.

Complexation between the Antioxidant Pterostilbene and Derivatized Cyclodextrins in the Solid State and in Aqueous Solution.

Inadequate aqueous solubilities of bioactive compounds hinder their ability to be developed for medicinal applications. The potent antioxidant pterostilbene (PTB) is a case in point. The aim of this study was to use a series of modified water-soluble cyclodextrins (CDs), namely, hydroxypropyl β-CD (HPβCD), dimethylated β-CD (DIMEB), randomly methylated β-CD (RAMEB), and sulfobutyl ether β-CD sodium salt (SBECD) to prepare inclusion complexes of PTB via various solid, semi-solid, and solution-based treatments. Putative CD-PTB products generated by solid-state co-grinding, kneading, irradiation with microwaves, and the evaporative treatment of CD-PTB solutions were considered to have potential for future applications. Primary analytical methods for examining CD-PTB products included differential scanning calorimetry and Fourier transform infrared spectroscopy to detect the occurrence of binary complex formation. Phase solubility analysis was used to probe CD-PTB complexation in an aqueous solution. Complexation was evident in both the solid-state and in solution. Complex association constants (K1:1) in an aqueous solution spanned the approximate range of 15,000 to 55,000 M-1; the values increased with the CDs in the order HPβCD < DIMEB < RAMEB < SBECD. Significant PTB solubility enhancement factors were recorded at 100 mM CD concentrations, the most accurately determined values being in the range 700-fold to 1250-fold.

Biophysics of IL-22 receptor interaction with selected interleukins.

Atopic dermatitis (AD) is the most prevalent chronic inflammatory skin condition globally, and many patients do not respond adequately to currently available therapies [1]. Interleukin-22 receptor 1 (IL-22RA1) has been identified as a potential mediator of AD, but no treatments for this pathway are currently on the market [2]. In this work, we aim to elucidate the biophysics of the binary and ternary IL-22RA1 complex formation with interleukins by combining surface plasmon resonance requiring protein immobilization and in-solution techniques such as small angle X-ray scattering and circular dichroism. In addition, structural characterization of the ternary complexes by high-resolution cryogenic electron microscopy is ongoing and will be used to provide Angstrom resolution structural data about the complexes. This will be coupled to molecular dynamics simulations, providing a comprehensive overview of the formation of IL-22RA1 signaling complexes resulting in knowledge on the domains involved in the signaling process. This will result in new and novel knowledge on the interaction with these interleukins and IL22R1 and provide insights into the role of these interleukins and potential approaches to block their interaction by an antibody approach.

Improved thermal stability of roselle anthocyanin by co-pigmented with oxalic acid: Preparation, characterization and enhancement mechanism

The enhancement effects of co-pigmentation on thermal stability of roselle anthocyanin extract (RAE) were investigated. The introduction of organic acids maintained color stability of RAE, and RAE co-pigmented with oxalic acid (OA) presented less color fading rates (19.46 ± 0.33 %) and higher redness (41.33 ± 3.51). Subsequently, suitable co-pigmentation concentration (OA:RAE = 1:2) was obtained regarding with lower ΔE (48.70 ± 2.36). Then, improvement behaviors of co-pigmentation on OA-RAE were evaluated. Results demonstrated that OA-RAE exhibited better thermal stability, as manifested by larger retention rates and more favorable thermal degradation kinetic parameters. Furthermore, both molecular docking simulation and experimental structural characterization revealed that hydrogen bonds and other non-covalent bonds made up the main parts of molecular interactions, leading to formation of stable binary complex. As a result, the aromatic ring of RAE was protected. In conclusion, the co-pigmentation of RAE via introduction of OA was effective in stability enhancement due to the generation of molecular bindings.

85 (PB075) - ASP3082, a First-in-class novel KRAS G12D degrader, exhibits remarkable anti-tumor activity in KRAS G12D mutated cancer models

Background: KRAS is one of the most frequently mutated oncogenes in various cancers. Among KRAS mutations, KRAS G12D is the most frequent driver mutation and is found in approximately 34% of pancreatic ductal adenocarcinoma (PDAC), 10% to 12% of colorectal cancer, 4% of lung adenocarcinoma and also in a subset of other solid tumors. However, there is no direct KRAS G12D-targeted inhibitors used in the clinical setting. Here, we identified ASP3082, a novel KRAS G12D degrader with high potency and selectivity. Methods: We investigated (1) binding affinity of ASP3082 to KRAS G12D protein and an E3 ligase in the conditions of binary complex and ternary complex formation using surface plasmon resonance assay, (2) degradation activity of ASP3082 on KRAS G12D protein using western blotting or in-cell western method, (3) inhibitory effect of ASP3082 on the growth of human cancer cells harboring KRAS G12D mutation and KRAS wild-type, (4) specificity for ASP3082-mediated degradation using proteomics approach, (5) antitumor activity of ASP3082 in mice subcutaneously xenografted with KRAS G12D-mutated pancreatic cancer cells, (6) PK-PD profile of ASP3082 after a single intravenous administration in the xenograft model. Results: ASP3082 directly bound to KRAS G12D-mutated protein and the E3 protein to form a ternary complex. Also, ASP3082 potently degraded KRAS G12D-mutated protein and inhibited phosphorylation of ERK in KRAS G12D-mutated pancreatic cancer cells. In addition, ASP3082 showed the growth inhibitory activity of KRAS G12D-mutated pancreatic cancer cells, but not of KRAS wildtype cancer cells. Furthermore, the quantitative proteomics analysis suggested that ASP3082 selectively degraded the KRAS G12D-mutated protein over other (>9000) proteins. in vivo experiment revealed that once-weekly intravenous administration of ASP3082 induced dose-dependent and significant growth inhibition of KRAS G12D PDAC tumors, resulting in profound tumor regression without body weight loss. ASP3082 showed sustained concentrations in the xenograft tumors after a single intravenous administration and decreased KRAS G12D-mutated protein levels according to the duration of the ASP3082 concentrations. Conclusions: ASP3082 is a potential therapeutic agent for patients with tumors harboring the KRAS G12D mutation. Currently, Phase I clinical trial is underway (NCT05382559). Conflict of interest: Corporate-sponsored Research: All authors are employees of Astellas Pharma Inc.

ENCAPSULATION OF EXEMESTANE WITH β-CYCLODEXTRIN AND TERNARY AGENT: FORMULATION, EVALUATION AND ANTICANCER ACTIVITY

Objective: A potent aromatase inhibitor, Exemestane, is well known for its anticancer action in breast neoplasm. The vital problem of this medicament is its poor aqueous solubility, which hinders its dissolution in body fluids. Therefore, the present study targets to enhance the water solubility of Exemestane by means of its complexation with β-cyclodextrin and a suitable ternary agent. Methods: Inclusion complexes of Exemestane with β-cyclodextrin and ternary agent were prepared by kneading and lyophilization technique. Different hydrophilic polymers and organic acids were screened for their influential ability as a co-complex with a carrier; β-cyclodextrin. The validation of complex formation was carried out by various solid-state techniques. The geometry of Exemestane in the β-cyclodextrin cavity was picturized in docking studies. The in vitro anticancer activity of prepared inclusion complex formulations carried out using MCF-7 cell lines Results: Phase solubility analysis proved HPMC E5 as the best ternary agent for complexation of Exemestane with β-cyclodextrin as it improved the stability constant of the drug from 665.92 M-1 to 1238.38 M-1. The synthesized binary and ternary inclusion complexes exhibited 2.74 and 4.62 times enhanced solubilization of Exemestane. Likewise, the dissolution characteristics of Exemestane were improved, and drug release was increased by 1.18 and 1.42 times with binary and ternary freeze-dried formulations. Differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) study results presented the formation of binary and ternary complexes with significantly drooped crystallinity. Docking studies predicted encapsulation of rings A, B, and C of Exemestane in the cavity of β-cyclodextrin. In-line results were obtained in Fourier transform infrared (FTIR) studies. The cell growth inhibition of 62.78 % was achieved with a ternary complex of Exemestane which was far superior than the pure active moiety that showed mere 44.56 % of inhibition. Conclusion: Altogether, it can be concluded that the inclusion complex of Exemestane boosted its aqueous solubility, resulting in its increased dissolution and in vitro anticancer activity in a breast cancer MCF-7 cell line.

Ternary System of Bacogenins with Fulvic Acid and Hydrogenated Soy Lecithin: Preparation, Characterization and, In vivo Studies.

The aim of this study was to simultaneously enhance the solubility and stability of bacogenins hydrolyzed bacoside rich extract by a ternary system comprised of hydrogenated soy lecithin and a third auxiliary substance, fulvic acid. Both ternary and binary complexes were prepared using the solvent evaporation method were characterized by Fourier transform infrared technique, differential scanning calorimeter and scanning electron microscope. The entrapment efficacy in both binary and ternary system was calculated and the effect on the solubility, dissolution and stability of bacogenins was found out. Furthermore, the prepared complexes were subjected to behavioural pharmacological studies. FTIR, DSC, and SEM studies in totality confirmed the formation of binary and ternary complexes. Enhancement in solubility was observed, and the order of release characteristics was found to be BHFS> BHSL>BHF> BH when the dissolution studies were carried out in 40% aqueous solution of ethanol. A significant improvement in the memory and antioxidant capacity was noticed in both binary, ternary complexes and fulvic acid treatment groups. The results revealed that the ternary complex could be a promising drug delivery system to improve the oral bioavailability of the bacogenins.

Inhibition mechanism of baicalein against alcohol dehydrogenase in vitro via biological techniques, spectroscopy and computer simulation

• Baicalein entered coenzyme cavity spontaneously to form a stable complex. • Activity of ADH was inhibited by baicalein in a non-competitive mechanism. • Baicalein altered the secondary structure of ADH and induced functional variation. • Decreased ASA of amino acid residues was the reason for fluorescence quenching. • Hydrogen bonds had been attested to be the vital forces for binary complex. Baicalein is a dietary flavonoid with extensive biological activity. Alcohol dehydrogenase (ADH) is one of the pivotal enzymes for alcohol metabolism. This research intends to investigate the mechanism of inhibition of ADH by baicalein and evaluate their structure–activity relationship. Baicalein inhibited ADH activity in a non-competitive manner. The fluorescence intensity of ADH decreased because of the formation of ADH-baicalein complex. Hydrogen bonds and van der Waals forces were the main acting forces in stabilising the complex. At 298 K, the binding constant (K a ) of baicalein to ADH was 5.41 × 10 4 L·mol −1 with one binding stoichiometry, suggesting formation of binary complex. Molecular docking analysis revealed that the hydroxyl groups on the side chain of baicalein interacted with ADH through hydrogen bonds. The interaction between baicalein and Val292 (B) may partially explain the decreased activity of ADH. The effect of baicalein on the structure of ADH was confirmed by three-dimensional (3D) fluorescence spectroscopy, circular dichroism (CD) spectroscopy, fourier-transform infrared (FT-IR) spectroscopy experiments and computer simulations. Overall, this study could reveal a novel research perspective on the therapeutic effect of baicalein and its medicinal value.

Allostery in the dynamic coactivator domain KIX occurs through minor conformational micro-states.

The coactivator KIX of CBP uses two binding surfaces to recognize multiple activators and exhibits allostery in ternary complex formation. Activator•coactivator interactions are central to transcriptional regulation, yet the microscopic origins of allostery in dynamic proteins like KIX are largely unknown. Here, we investigate the molecular recognition and allosteric manifestations involved in two KIX ternary systems c-Myb•KIX•MLL and pKID•KIX•MLL. Exploring the hypothesis that binary complex formation prepays an entropic cost for positive cooperativity, we utilize molecular dynamics simulations, side chain methyl order parameters, and differential scanning fluorimetry (DSF) to explore conformational entropy changes in KIX. The protein’s configurational micro-states from structural clustering highlight the utility of protein plasticity in molecular recognition and allostery. We find that apo KIX occupies a wide distribution of lowly-populated configurational states. Each binding partner has its own suite of KIX states that it selects, building a model of molecular recognition fingerprints. Allostery is maximized with MLL pre-binding, which corresponds to the observation of a significant reduction in KIX micro-states observed when MLL binds. With all binding partners, the changes in KIX conformational entropy arise predominantly from changes in the most flexible loop. Likewise, we find that a small molecule and mutations allosterically inhibit/enhance activator binding by tuning loop dynamics, suggesting that loop-targeting chemical probes could be developed to alter KIX•activator interactions. Experimentally capturing KIX stabilization is challenging, particularly because of the disordered nature of particular activators. However, DSF melting curves allow for inference of relative entropic changes that occur across complexes, which we compare to our computed entropy changes using simulation methyl order parameters.

Complexation of pillar[5]arene-based Schiff bases with methylene blue: Formation of binary complexes with improved anticancer activity

Cocktail therapy is one of the leading approaches for treating some complex diseases. Herein, a pH-triggered supramolecular cocktail drug delivery system assembled by the medium-strength complexes of pillar[5]arene-based Schiff base (P5SB) with methylene blue (MB). Molecular modeling suggest that noncovalent interactions between Schiff base side chain of P5SB and MB were mainly responsible for the stability of the complex. The amphiphilic P5SB⊃MB complex assembled into stable vesicles with an average diameter of 244.1 nm in conventional physiological environment (pH=7.4). Drug loading experiments demonstrated that doxorubicin (DOX) could be efficiently encapsulated into the hollow vesicles, and the drug would be rapidly released under acidic environment (pH=6.0). Moreover, the anti-cancer efficiency of DOX-loaded P5SB⊃MB vesicles was significantly enhanced because of the synergistic effect of P5SB, MB and DOX. Nonetheless, the live-cell imaging property of DOX was maintained after encapsulation.

Solubility of Ca(II), Ni(II), Nd(III) and Pu(IV) in the presence of proxy ligands for the degradation of polyacrylonitrile in cementitious systems.

The solubility of Ca(OH)2(cr), β-Ni(OH)2(cr), Nd(OH)3(s) and PuO2(ncr, hyd) was investigated in cement porewater solutions containing glutarate (GTA), α-hydroxyisobutarate (HIBA) and 3-hydroxybutarate (HBA). These ligands were proposed as probable degradation products of UP2W, a polyacrylonitrile-based filter aid used in nuclear power plants. Results obtained in this work are compared with reported solubility data in the presence of iso-saccharinic acid (ISA), a polyhydroxocarboxylic acid resulting from cellulose degradation. None of the investigated proxy ligands shows any significant impact on the solubility of Ca(II), Nd(III) or Pu(IV) in cement porewater solutions. Although the formation of binary complexes M-L (M = Ca(II), Nd(III), An(IV); L = GTA, HIBA, HBA) under acidic conditions is described in the literature, these organic ligands cannot outcompete hydrolysis under hyperalkaline conditions. GTA, HIBA and HBA induce a slight increase in the solubility of β-Ni(OH)2(cr) at [L]tot = 0.1 M. This observation supports the formation of stable Ni(II)-GTA, -HIBA and -HBA complexes in hyperalkaline conditions, although the exact stoichiometry of these complexes remains unknown. The comparison of these results with solubility data in the presence of ISA confirms the stronger complexation properties of the latter ligand. Even though HIBA and HBA are carboxylic acids containing one alcohol group, this comparison shows that additional alcohol groups are required to efficiently chelate the metal ion and outcompete hydrolysis. This conclusion is supported by DFT calculations on the Pu(IV)-OH-L systems (L = GTA, HIBA and HBA), which indicate that the complexation with the proxy ligands takes places through the carboxylate group. XRD of selected solid phases after equilibration with proxy ligands at [L]tot = 0.1 M confirms that Ca(II), Ni(II), Nd(III) and Pu(IV) starting solid materials remained mostly unaltered in the course of the experiments. However, the presence of new XRD features suggests the possible formation of secondary phases. These results allow assessment of the effect of the proposed proxy ligands on the solubility of key radionuclides and metal ions in cementitious systems relevant for low and intermediate level waste, and feed into on-going sorption studies evaluating the impact of UP2W degradation products on the uptake of radionuclides by cement.

Determination of Stability Constant of The Complexes of Metal Ion Fe(III), Mn(II) And Cr(III) With Some Substituted 2-Oxo-2H-Chromene-3-Carbohydrazide Derivatives at 0.1 M Ionic Strength at 42oC

Proton ligand and metal ligand stability constant are measured for Fe(III) and 1, 2-dihydroxy benzene and 1, 5-disulphonic acid complexes . Determination of stability constant of substituted of pyrazoles with rare earth metals form complexes are reported . Effect of temperature on formation constants of 2 acetylpyridine(N benzoyl)glycine hydrazone with lanthanide(III) ions at different ionic strengths are reported. Irving and Rossotti, Herson and Gilbert , Wilkins and Lewis and Rossotti and Rossotti have determined stability constant by Bjerrum-Calvin titration technique . Kabadi , Jahagirdar and Narwade have determined pK values of salicylaldehyde, salicylic acid and sulphonic acid respectively by similar procedure. The metal ligand stability constant of some β-diketones are reported . Stability constants have investigated for some substituted pyrazolines, isoxalline and diketone . The method most frequently applied for study of complex equilibria is pH-metric titration technique . Stepwise formation of mononuclear binary complexes is described by set of equilibrium constants. For pH-metric measurements an electrode must be selected. According to Bjerrum, Martell and Calvin , the formation of complex MLN is stepwise process and one has to deal with a series of equilibria of the type: Irving and Rossotti, Herson and Gilbert , Wilkins and Lewis and Rossotti and Rossotti have determined stability constant by Calvin-Bjerrum titration technique . The value of nA,n, pK, log K1 and log K2 are evaluated by Irving and Rossotti's equation. The stability constant and thermodynamic parameters of complexes containing lighter lanthanides , copper(II) , calcium and magnesium are reported. It is also important in environmental studies , medicinal and industrial chemistry . Effects of transition metal on stability constant of complexes have studied by pH metric method . Bendi , Janrao and Ramteke have studied stability constant of ligands with lanthanide metals complexes.The present work involves pH metric study of substituted 2-oxo-2H-chromene-3-carbohydrazide derivatives with metal ions Fe(III), Mn(II), Cr(III) and Ti(III) at temperature42oC. The Bjerrum-Calvin titration technique as modified by Irving and Rossotti has been employed in the present study. The following three sets of titrations are carried out in sequence.

Inhibition mechanisms of CRISPR-Cas9 by AcrIIA17 and AcrIIA18.

Mobile genetic elements such as phages and plasmids have evolved anti-CRISPR proteins (Acrs) to suppress CRISPR-Cas adaptive immune systems. Recently, several phage and non-phage derived Acrs including AcrIIA17 and AcrIIA18 have been reported to inhibit Cas9 through modulation of sgRNA. Here, we show that AcrIIA17 and AcrIIA18 inactivate Cas9 through distinct mechanisms. AcrIIA17 inhibits Cas9 activity through interference with Cas9-sgRNA binary complex formation. In contrast, AcrIIA18 induces the truncation of sgRNA in a Cas9-dependent manner, generating a shortened sgRNA incapable of triggering Cas9 activity. The crystal structure of AcrIIA18, combined with mutagenesis studies, reveals a crucial role of the N-terminal β-hairpin in AcrIIA18 for sgRNA cleavage. The enzymatic inhibition mechanism of AcrIIA18 is different from those of the other reported type II Acrs. Our results add new insights into the mechanistic understanding of CRISPR-Cas9 inhibition by Acrs, and also provide valuable information in the designs of tools for conditional manipulation of CRISPR-Cas9.

Characterization of toxicity and structure of PirABvc -like proteins that are structurally almost identical to shrimp AHPND-causing PirAB toxin.

PirAB is a binary toxic protein that causes acute hepatopancreatic necrosis disease (AHPND) in shrimp. Their closest homologs, PirAvc -like and PirBvc -like proteins, are encoded by two adjacent genes on a non-pVH plasmid from a Vibrio campbellii strain. Herein, PirABvc -like protein caused neither abnormalities nor death in shrimp postlarvae (Litopenaeus vannamei); furthermore, typical AHPND clinical signs were not observed. PirAvc -like protein corresponds to Cry toxin domain III (ligand-binding domain) and likely binds to N-acetylgalactosamine. The C-terminal and N-terminal of PirBvc -like resemble Cry toxin domain II (receptor-binding domain) and domain I (pore-forming domain), respectively. PirAvc -like and PirBvc -like proteins are structurally similar to PirA and PirB, respectively. Subtle structural differences between PirAvc -like protein and PirA appear to be involved in ligand-binding and binary protein complex formation. The difference in virulence of PirABvc -like and PirAB may result from the specific binding of the protein complex to distinct host receptors. These results shed light on the potential functions and host receptors of PirABvc -like proteins and their relationship with PirAB.