scholarly journals The Application of Reversible Intramolecular Sulfonamide Ligation to Modulate Reactivity in Organometallic Ruthenium(II) Diamine Complexes

Molecules ◽  
2020 ◽  
Vol 25 (2) ◽  
pp. 244
Author(s):  
Samuel A. Kemp ◽  
Timothy J. Prior ◽  
Huguette Savoie ◽  
Ross W. Boyle ◽  
Benjamin S. Murray
Keyword(s):  
Healthy Tissue ◽  
Central Metal Atom ◽  
Dependent Manner ◽  
Central Metal ◽  
Coordination Environment ◽  
Typical Cell ◽  
Arene Ligand ◽  
Ph Conditions ◽  
Ph Dependent

Metallation of biomacromolecular species forms the basis for the anticancer activity of many metallodrugs. A major limitation of these compounds is that their reactivity is indiscriminate and can, in principle, occur in healthy tissue as well as cancerous tissue, potentially leading to side effects in vivo. Here we present pH-dependent intramolecular coordination of an arene-tethered sulfonamide functionality in organometallic ruthenium(II) ethylenediamine complexes as a route to controlling the coordination environment about the central metal atom. Through variation of the sulfonamide R group and the length of the tether linking it to the arene ligand the acidity of the sulfonamide NH group, and hence the pH-region over which regulation of metal coordination occurs, can be modulated. Intramolecular sulfonamide ligation controlled the reactivity of complex 4 within the physiologically relevant pH-region, rendering it more reactive towards 5ʹ-GMP in mildly acidic pH-conditions typical of tumour tissue compared to the mildly alkaline pH-conditions typical of healthy tissue. However, the activation of 4 by ring-opening of the chelate was found to be a slow process relative to the timescale of typical cell culture assays and members of this series of complexes were found not to be cytotoxic towards the HT-29 cell line. These complexes provide the basis for the development of analogues of increased potency where intramolecular sulfonamide ligation regulates reactivity and therefore cytotoxicity in a pH-dependent, and potentially, tissue-dependent manner.

scholarly journals Arabidopsis thaliana Plant Natriuretic Peptide Active Domain Forms Amyloid-like Fibrils in a pH-Dependent Manner

Plants ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 9
Author(s):  
Georgia I. Nasi ◽  
Foteini D. Aktypi ◽  
Panagiotis M. Spatharas ◽  
Nikolaos N. Louros ◽  
Paraskevi L. Tsiolaki ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Amyloid Fibrils ◽  
Dependent Manner ◽  
Amyloidogenic Proteins ◽  
Transmission Electron ◽  
Ft Ir ◽  
Ph Conditions ◽  
Ph Dependent ◽  
Ft Ir Spectroscopy

Plant natriuretic peptides (PNPs) are hormones that have been extracted from many different species, with the Arabidopsis thaliana PNP (AtPNP-A) being the most studied among them. AtPNP-A is a signaling molecule that consists of 130 residues and is secreted into the apoplast, under conditions of biotic or abiotic stress. AtPNP-A has distant sequence homology with human ANP, a protein that forms amyloid fibrils in vivo. In this work, we investigated the amyloidogenic properties of a 34-residue-long peptide, located within the AtPNP-A sequence, in three different pH conditions, using transmission electron microscopy, X-ray fiber diffraction, ATR FT-IR spectroscopy, Congo red and Thioflavin T staining assays. We also utilize bioinformatics tools to study its association with known plant amyloidogenic proteins and other A. thaliana proteins. Our results reveal a new case of a pH-dependent amyloid forming peptide in A. thaliana, with a potential functional role.

scholarly journals Siderophore-mediated zinc acquisition enhances enterobacterial colonization of the inflamed gut

2020 ◽  
Author(s):  
Hui Zhi ◽  
Judith Behnsen ◽  
Allegra Aron ◽  
Vivekanandan Subramanian ◽  
Janet Z. Liu ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Local Environment ◽  
Probiotic Bacterium ◽  
Zinc Transporters ◽  
Bacterial Metabolism ◽  
Dependent Manner ◽  
Metal Affinity ◽  
Ph Dependent

ABSTRACTZinc is an essential cofactor for bacterial metabolism, and many Enterobacteriaceae express the zinc transporters ZnuABC and ZupT to acquire this metal in the host. Unexpectedly, the probiotic bacterium Escherichia coli Nissle 1917 exhibited appreciable growth in zinc-limited media even when these transporters were deleted. By utilizing in vitro and in vivo studies, as well as native spray metal infusion mass spectrometry and ion identity molecular networking, we discovered that Nissle utilizes yersiniabactin as a zincophore. Indeed, yersiniabactin enables Nissle to scavenge zinc in zinc-limited media, to resist calprotectin-mediated zinc sequestration, and to thrive in the inflamed gut. Moreover, we discovered that yersiniabactin’s affinity for iron or zinc changes in a pH-dependent manner, with higher affinity for zinc as the pH increased. Altogether, we demonstrate that siderophore metal affinity can be influenced by the local environment and reveal a mechanism of zinc acquisition available to many commensal and pathogenic Enterobacteriaceae.

scholarly journals A Triple Helix within a Pseudoknot Is a Conserved and Essential Element of Telomerase RNA

2007 ◽  
Vol 27 (6) ◽  
pp. 2130-2143 ◽  
Author(s):  
Kinneret Shefer ◽  
Yogev Brown ◽  
Valentin Gorkovoy ◽  
Tamar Nussbaum ◽  
Nikolai B. Ulyanov ◽  
...  
Keyword(s):  
Triple Helix ◽  
Kluyveromyces Lactis ◽  
Three Dimensional ◽  
Essential Element ◽  
Proliferative Potential ◽  
Telomerase Rna ◽  
Dependent Manner ◽  
Pseudoknot Structure ◽  
Ph Dependent

ABSTRACT Telomerase copies a short template within its integral telomerase RNA onto eukaryotic chromosome ends, compensating for incomplete replication and degradation. Telomerase action extends the proliferative potential of cells, and thus it is implicated in cancer and aging. Nontemplate regions of telomerase RNA are also crucial for telomerase function. However, they are highly divergent in sequence among species, and their roles are largely unclear. Using in silico three-dimensional modeling, constrained by mutational analysis, we propose a three-dimensional model for a pseudoknot in telomerase RNA of the budding yeast Kluyveromyces lactis. Interestingly, this structure includes a U-A·U major-groove triple helix. We confirmed the triple-helix formation in vitro using oligoribonucleotides and showed that it is essential for telomerase function in vivo. While triplex-disrupting mutations abolished telomerase function, triple compensatory mutations that formed pH-dependent G-C·C+ triples restored the pseudoknot structure in a pH-dependent manner and partly restored telomerase function in vivo. In addition, we identified a novel type of triple helix that is formed by G-C·U triples, which also partly restored the pseudoknot structure and function. We propose that this unusual structure, so far found only in telomerase RNA, provides an essential and conserved telomerase-specific function.

scholarly journals Engineering a Monomeric Fc Domain Modality by N-Glycosylation for the Half-life Extension of Biotherapeutics

2013 ◽  
Vol 288 (23) ◽  
pp. 16529-16537 ◽  
Author(s):  
Tetsuya Ishino ◽  
Mengmeng Wang ◽  
Lidia Mosyak ◽  
Amy Tam ◽  
Weili Duan ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Tandem Repeat ◽  
Half Life ◽  
Fusion Proteins ◽  
Life Extension ◽  
Dependent Manner ◽  
Neonatal Fc Receptor ◽  
Dimer Interface ◽  
Ph Dependent

Human IgG is a bivalent molecule that has two identical Fab domains connected by a dimeric Fc domain. For therapeutic purposes, however, the bivalency of IgG and Fc fusion proteins could cause undesired properties. We therefore engineered the conversion of the natural dimeric Fc domain to a highly soluble monomer by introducing two Asn-linked glycans onto the hydrophobic CH3-CH3 dimer interface. The monomeric Fc (monoFc) maintained the binding affinity for neonatal Fc receptor (FcRn) in a pH-dependent manner. We solved the crystal structure of monoFc, which explains how the carbohydrates can stabilize the protein surface and provides the rationale for molecular recognition between monoFc and FcRn. The monoFc prolonged the in vivo half-life of an antibody Fab domain, and a tandem repeat of the monoFc further prolonged the half-life. This monoFc modality can be used to improve the pharmacokinetics of monomeric therapeutic proteins with an option to modulate the degree of half-life extension.

scholarly journals A Novel Formulation of Cisplatin with γ-Polyglutamic Acid and Chitosan Reduces Its Adverse Renal Effects: An In Vitro and In Vivo Animal Study

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1803
Author(s):  
Masao Sasai ◽  
Kazuma Sakura ◽  
Takayuki Matsuda ◽  
Hiroshi Uyama
Keyword(s):  
Renal Damage ◽  
Chemotherapeutic Agent ◽  
In Vitro Cytotoxicity ◽  
Dependent Manner ◽  
Polyglutamic Acid ◽  
Ph Dependent ◽  
Dose Dependent ◽  
Target Effects

Cisplatin (cis-diamminedichloroplatinum (II); CDDP) is a key chemotherapeutic agent but causes renal damage and other off-target effects. Here, we describe the pharmacological and biochemical characteristics of a novel formulation of CDDP complexed with γ-polyglutamic acid (γ-PGA) and chitosan (CS), γ-PGA/CDDP-CS, developed by complexing CDDP with γ-PGA, then adding CS (15 kDa; 10 mol%/γ-PGA). We analyzed tumor cytotoxicity in vitro, as well as blood kinetics, acute toxicity, and antitumor efficacy in vivo in BALB/cAJcl mice. γ-PGA/CDDP-CS showed pH-dependent release in vitro over 12 days (9.1% CDDP released at pH 7.4; 49.9% at pH 5.5). It showed in vitro cytotoxicity in a dose-dependent manner similar to that of uncomplexed CDDP. In a mesothelioma-bearing mouse model, a 15 mg/kg dose of CDDP inhibited tumor growth regardless of the type of formulation, complexed or uncomplexed; however, all mice in the uncomplexed CDDP group died within 13 days. γ-PGA/CDDP-CS was as effective as free CDDP in vivo but much less toxic.

scholarly journals The Erv41–Erv46 complex serves as a retrograde receptor to retrieve escaped ER proteins

2015 ◽  
Vol 208 (2) ◽  
pp. 197-209 ◽  
Author(s):  
Aya Shibuya ◽  
Neil Margulis ◽  
Romain Christiano ◽  
Tobias C. Walther ◽  
Charles Barlowe
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Complex I ◽  
Secretory Pathway ◽  
Isotope Labeling ◽  
Dependent Manner ◽  
Bafilomycin A1 ◽  
Early Secretory Pathway ◽  
Ph Dependent

Signal-dependent sorting of proteins in the early secretory pathway is required for dynamic retention of endoplasmic reticulum (ER) and Golgi components. In this study, we identify the Erv41–Erv46 complex as a new retrograde receptor for retrieval of non–HDEL-bearing ER resident proteins. In cells lacking Erv41–Erv46 function, the ER enzyme glucosidase I (Gls1) was mislocalized and degraded in the vacuole. Biochemical experiments demonstrated that the luminal domain of Gls1 bound to the Erv41–Erv46 complex in a pH-dependent manner. Moreover, in vivo disturbance of the pH gradient across membranes by bafilomycin A1 treatment caused Gls1 mislocalization. Whole cell proteomic analyses of deletion strains using stable isotope labeling by amino acids in culture identified other ER resident proteins that depended on the Erv41–Erv46 complex for efficient localization. Our results support a model in which pH-dependent receptor binding of specific cargo by the Erv41–Erv46 complex in Golgi compartments identifies escaped ER resident proteins for retrieval to the ER in coat protein complex I–formed transport carriers.

Current Status of and Recent Results on Group 2 Source Compounds for Vapor Phase Epitaxy of Ferroelectric Thin Films

1993 ◽  
Vol 310 ◽  
Author(s):  
William S. Rees ◽  
Henry A. Luten ◽  
Michael W. Carris ◽  
Celia R. Caballero ◽  
Werner Hesse ◽  
...  
Keyword(s):  
Thin Films ◽  
Ferroelectric Thin Films ◽  
Current Status ◽  
Central Metal Atom ◽  
Central Metal ◽  
Coordination Environment ◽  
Advantages And Disadvantages ◽  
Recent Developments ◽  
High Vapor ◽  
Group 2

AbstractMuch interest in the area of ferroelectric thin films has been generated by the recent developments in unique property observation for these materials. As deposition methods move toward potential commercialization, the importance of chemically and thermally stable at use temperature, high vapor pressure and purity, readily available and economically competitive sources for the requisite group 2 elements will emerge. This presentation entails an initial overview of the presently utilized compounds, their advantages and disadvantages. New group 2 CVD precursors have been developed based both on inter- and intramolecular stabilization of cyclopentadienides, alkoxides and β-diketonates. Recent results on the coordination environment around the central metal atom have offered insight into the next generation of polydentate, monoanionic ligand design. Specific details are discussed for the metal complexes of “scorpion-tail” β-diketoethers. Results of comparison studies between these new precursors and earlier compounds are presented as a model for designing future sources.

Effects of NO-Donors on Thrombus Formation and Microcirculation in Cerebral Vessels of the Rat

1996 ◽  
Vol 76 (01) ◽  
pp. 111-117 ◽  
Author(s):  
Yasuto Sasaki ◽  
Junji Seki ◽  
John C Giddings ◽  
Junichiro Yamamoto
Keyword(s):  
Blood Flow ◽  
Thrombus Formation ◽  
Dependent Manner ◽  
Red Cell ◽  
Cell Velocity ◽  
Red Cell Velocity ◽  
The Mean ◽  
Wall Shear ◽  
Dose Dependent

SummarySodium nitroprusside (SNP) and 3-morpholinosydnonimine (SIN-1), are known to liberate nitric oxide (NO). In this study the effects of SNP and SIN-1 on thrombus formation in rat cerebral arterioles and venules in vivo were assessed using a helium-neon (He-Ne) laser. SNP infused at doses from 10 Μg/kg/h significantly inhibited thrombus formation in a dose dependent manner. This inhibition of thrombus formation was suppressed by methylene blue. SIN-1 at a dose of 100 Μg/kg/h also demonstrated a significant antithrombotic effect. Moreover, treatment with SNP increased vessel diameter in a dose dependent manner and enhanced the mean red cell velocity measured with a fiber-optic laser-Doppler anemometer microscope (FLDAM). Blood flow, calculated from the mean red cell velocity and vessel diameters was increased significantly during infusion. In contrast, mean wall shear rates in the arterioles and venules were not changed by SNP infusion. The results indicated that SNP and SIN-1 possessed potent antithrombotic activities, whilst SNP increased cerebral blood flow without changing wall shear rate. The findings suggest that the NO released by SNP and SIN-1 may be beneficial for the treatment and protection of cerebral infarction

The Effect of Active Site-inhibited Factor VIIa on Tissue Factor-initiated Coagulation Using Platelets before and after Aspirin Administration

1997 ◽  
Vol 78 (04) ◽  
pp. 1202-1208 ◽  
Author(s):  
Marianne Kjalke ◽  
Julie A Oliver ◽  
Dougald M Monroe ◽  
Maureane Hoffman ◽  
Mirella Ezban ◽  
...  
Keyword(s):  
Tissue Factor ◽  
Active Site ◽  
Large Scale ◽  
Thrombin Generation ◽  
Factor Viia ◽  
Dependent Manner ◽  
Antithrombotic Agent ◽  
Before And After ◽  
Ic50 Values

SummaryActive site-inactivated factor VIIa has potential as an antithrombotic agent. The effects of D-Phe-L-Phe-L-Arg-chloromethyl ketone-treated factor VIla (FFR-FVIIa) were evaluated in a cell-based system mimicking in vivo initiation of coagulation. FFR-FVIIa inhibited platelet activation (as measured by expression of P-selectin) and subsequent large-scale thrombin generation in a dose-dependent manner with IC50 values of 1.4 ± 0.8 nM (n = 8) and 0.9 ± 0.7 nM (n = 7), respectively. Kd for factor VIIa binding to monocytes ki for FFR-FVIIa competing with factor VIIa were similar (11.4 ± 0.8 pM and 10.6 ± 1.1 pM, respectively), showing that FFR-FVIIa binds to tissue factor in the tenase complex with the same affinity as factor VIIa. Using platelets from volunteers before and after ingestion of aspirin (1.3 g), there were no significant differences in the IC50 values of FFR-FVIIa [after aspirin ingestion, the IC50 values were 1.7 ± 0.9 nM (n = 8) for P-selectin expression, p = 0.37, and 1.4 ± 1.3 nM (n = 7) for thrombin generation, p = 0.38]. This shows that aspirin treatment of platelets does not influence the inhibition of tissue factor-initiated coagulation by FFR-FVIIa, probably because thrombin activation of platelets is not entirely dependent upon expression of thromboxane A2.

Rationalizing the pH-Activity Response for Escherichia Coli’s Glycinamide Ribonucleotidetransformylase Through Computational Methods

2019 ◽  
Author(s):  
Adrian Roitberg ◽  
Pancham Lal Gupta
Keyword(s):  
Transfer Reaction ◽  
Catalytic Mechanism ◽  
Ph Dependence ◽  
Ph Effects ◽  
Dependent Manner ◽  
E Coli ◽  
Gar Tfase ◽  
Activity Curve ◽  
Ph Dependent ◽  
Formyl Transfer

<div>Human Glycinamide ribonucleotide transformylase (GAR Tfase), a regulatory enzyme in the de novo purine biosynthesis pathway, has been established as an anti-cancer target. GAR Tfase catalyzes the formyl transfer reaction from the folate cofactor to the GAR ligand. In the present work, we study E. coli GAR Tfase, which has high sequence similarity with the human GAR Tfase with most functional residues conserved. E. coli GAR Tfase exhibits structural changes and the binding of ligands that varies with pH which leads to change the rate of the formyl transfer reaction in a pH-dependent manner. Thus, the inclusion of pH becomes essential for the study of its catalytic mechanism. Experimentally, the pH-dependence of the kinetic parameter kcat is measured to evaluate the pH-range of enzymatic activity. However, insufficient information about residues governing the pH-effects on the catalytic activity leads to ambiguous assignments of the general acid and base catalysts and consequently its catalytic mechanism. In the present work, we use pH-replica exchange molecular dynamics (pH-REMD) simulations to study the effects of pH on E. coli GAR Tfase enzyme. We identify the titratable residues governing the pH-dependent conformational changes in the system. Furthermore, we filter out the protonation states which are essential in maintaining the structural integrity, keeping the ligands bound and assisting the catalysis. We reproduce the experimental pH-activity curve by computing the population of key protonation states. Moreover, we provide a detailed description of residues governing the acidic and basic limbs of the pH-activity curve.</div>

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