Bromo-Substituted Diazenyl-pyrazolo[1,5-a]pyrimidin-2-amines: Sonogashira Cross-Coupling Reaction, Photophysical Properties, Bio-interaction and HSA Light-Up Sensor.

A convenient synthesis of a broad series of thirteen examples of alkyne-spacer derivatives 2 from the well-known Sonogashira cross-coupling reaction on diazenyl-pyrazolo[1,5-a]pyrimidin-2-amine compounds 1 is reported. The reactivity of heterocycles 1 due the presence of selected electron-donor (EDG) and electron-withdrawing (EWG) groups attached to different alkynes was evaluated. Also, the reactional versatility due the position variation of the bromo atom at the scaffolds 1 was also investigated. In general, derivatives presented strong absorption bands at the 250-500 nm optical window and UV to cyan emission properties. Also, the redox analysis was recorded by electrochemical cyclic voltammetry technique. For HSA biomacromolecule assays, spectroscopic studies by UV-Vis, steady-state and time-resolved emission fluorescence, and molecular docking calculations evidenced the ability of each compound to establish interactions with human serum albumin (HSA). Finally, the behavior presented for this new class of heterocycles makes them a promising tool as optical sensors for albumins.

Chemotactic selection of frozen-thawed stallion sperm improves sperm quality and heterologous binding to oocytes.

The successful use of assisted reproduction techniques (ART) depends in part on the sperm physiological status. Several sperm selection procedures have been applied to improve quality of sperm population when using the ART. There has previously been development of a Sperm Selection Assay (SSA) for humans which is based on the attraction of capacitated sperm by chemotaxis towards progesterone (P), resulting in an enriched sperm population with an optimal physiological status similar to capacitated spermatozoa, with these cells having very little DNA fragmentation and optimal concentrations of reactive oxygen species (ROS). In the present study, the aim was to adapt the SSA for frozen-thawed stallion semen samples and evaluate the functional status of those sperm selected using the SSA procedure, and to determine whether this enriched sperm population has a greater capacity to bind to the zona pellucida of cattle oocytes. There were experimental conditions developed to conduct the SSA with stallion sperm. Using these conditions, the indexes of induced acrosome reaction, protein tyrosine phosphorylation, mitochondrial membrane potential, mitochondrial and cytoplasmic reactive oxygen species, and number of sperm bound to the zona pellucida of cattle were greater when the sperm population was selected using the SSA. Consistently, the DNA fragmentation and phospholipase C zeta indexes were less for the selected sperm. In conclusion, stallion sperm selected using chemotaxis utilizing the SSA provides a sperm population of greater quality, which when used may improve the outcomes with use of the ART.

Production and Characterization of MIC1: A Lectin from Toxoplasma gondii.

Some lectins of pathogens interact with host cells through the recognition of specific carbohydrates displayed on the mammals' cell surface. The microneme protein 1 (MIC1) from Toxoplasma gondii has a lectin domain that specifically binds sialic acid residues, often found in the terminal positions of N-glycans of mammalian cells. The necessary studies on the MIC1 biological roles have been limited initially by the laborious purification of the protein from T. gondii tachyzoites and the low yields verified. Then Escherichia coli has been transformed with a construct containing the MIC1 gene, and the obtained recombinant MIC1 (rMIC1) has been purified from the inclusion bodies. Herein, we detail the methodology of heterologous production and purification of rMIC1 and protocols to assay the rMIC1 lectin ability.

Assessment of different sperm functional tests in golden-headed lion tamarins (Leontopithecus chrysomelas).

The golden-headed lion tamarin (Leontopithecus chrysomelas) is an endangered species endemic to Brazil's Atlantic Forest, a shrinking biodiversity hotspot. As in other Neotropical primates, its semen characteristics and freezability are poorly studied. Hence, reproductive technologies for callitrichids would greatly benefit from reliable methods of semen analysis. In a bid to promote reproductive research in tamarins, we validated simple and inexpensive sperm function tests that can be used to monitor sperm-egg binding, plasma membrane and acrosome integrity, mitochondrial activity, and DNA fragmentation. Ejaculates from adult males were individually diluted and divided into control and damage-induced aliquots, and then samples comprising assorted amounts of damaged spermatozoa were examined by organelle-specific tests. Our findings showed that sperm-binding in chicken egg perivitelline membrane (EPM) positively correlated with the number of spermatozoa injured by snap-freezing. Eosin-nigrosin (EN) and propidium iodide readings were correlated with each other, and both provided robust measurements of plasma membrane integrity. A high correlation between expected and measured amounts of acrosome-intact spermatozoa was found using Fast Green-Rose Bengal (FG-RB), Coomassie Blue (CB), and FITC-PSA stains, and all three methods exhibited comparable results. Likewise, different percentages of UV-irradiated spermatozoa were accurately assessed for DNA integrity by Toluidine Blue (TB) and sperm chromatin dispersion (SCD) tests. Comparisons between 3,3'-diaminobenzidine (DAB) and JC-1 stains also indicated the reliability of the former assay to ascertain gradual increases in spermatozoa with greater mitochondrial function. These data confirmed that different parts of the tamarin spermatozoa can be simply and consistently evaluated by EPM, EN, FG-RB, CB, TB, and DAB protocols.

Morphology, toxicity and molecular characterization of Gambierdiscus spp. towards risk assessment of ciguatera in south central Cuba.

Ciguatera poisoning is caused by the consumption of reef fish or shellfish that have accumulated ciguatoxins, neurotoxins produced by benthic dinoflagellates of the genera Gambierdiscus or Fukuyoa. Although ciguatera constitutes the primary cause of seafood intoxication in Cuba, very little information is available on the occurrence of ciguatoxins in the marine food web and the causative benthic dinoflagellate species. This study conducted on the south-central coast of Cuba reports the occurrence of Gambierdiscus and Fukuyoa genera and the associated benthic genera Ostreopsis and Prorocentrum. Gambierdiscus/Fukuyoa cells were present at low to moderate abundances depending on the site and month of sampling. This genus was notably higher on Dictyotaceae than on other macrophytes. PCR analysis of field-collected samples revealed the presence of six different Gambierdiscus and one Fukuyoa species, including G. caribaeus, G. carolinianus, G. carpenteri, G. belizeanus, F. ruetzleri, G. silvae, and Gambierdiscus sp. ribotype 2. Only Gambierdiscus excentricus was absent from the eight Gambierdiscus/Fukuyoa species known in the wider Caribbean region. Eleven clonal cultures were established and confirmed by PCR and SEM as being either G. carolinianus or G. caribaeus. Toxin production in each isolate was assessed by a radioligand receptor binding assay and found to be below the assay quantification limit. These novel findings augment the knowledge of the ciguatoxin-source dinoflagellates that are present in Cuba, however further studies are needed to better understand the correlation between their abundance, species-specific toxin production in the environment, and the risk for fish contamination, in order to develop better informed ciguatera risk management strategies.

Heterologous expression and functional characterization of the ligand-binding domain of oxysterol-binding protein from Aspergillus oryzae.

Oxysterol-binding proteins (OSBPs) comprise a family of sterol-binding proteins. In this study, we focused on AoOSBP1, one of the five OSBP proteins identified from the industrial fungus Aspergillus oryzae. The temporal expression pattern analysis showed that the expression of AoOSBP1, in both gene and protein levels, was stably expressed throughout the developmental stages, while was upregulated during the accelerated growth stage. The immunofluorescence observation revealed that AoOSBP1 protein was mainly distributed in the conidiophore, indicating its underlying role in spore formation. The ligand-binding domain of AoOSBP1, namely OSBP-related domain (ORD), was heterologously expressed in Escherichia coli and purified. The binding assay carried out using microscale thermophoresis showed that the recombinant AoORD protein exhibited binding affinity for ergosterol, and exhibited much higher affinity to oxysterols (25-hydroxycholesterol and 7-ketocholesterol) and phytosterols (ß-sitosterol and stigmasterol). By contrast, MBP tag as the negative control showed no binding affinity for sterols. The present work demonstrates that AoORD domain in AoOSBP1 is capable of binding sterols, plays an underlying role in sterols transportation, and may participate in spore formation.

Label-free evaluation of small-molecule-protein interaction using magnetic capture and electrochemical detection.

The evaluation of interaction between small molecules and protein is an important step in the discovery of new drugs and to study complex biological systems. In this work, an alternative method was presented to evaluate small-molecule-protein interaction by using ligand capture by protein-coated magnetic particles (MPs) and disposable electrochemical cells. The interaction study was conducted using [10]-gingerol from ginger rhizome and a transmembrane protein αVß3 integrin. Initially, the electrochemical behavior of the natural compound [10]-gingerol was evaluated with the disposable carbon-based electrodes and presented an irreversible oxidation process controlled by diffusion. The analytical curve for [10]-gingerol was obtained in the range of 1.0 to 20.0 µmol L-1, with limit of detection of 0.26 µmol L-1. Then MPs coated with αVß3 integrin were incubated with standard solutions and extracts of ginger rhizome for [10]-gingerol capture and separation. The bioconjugate obtained was dropped to the disposable electrochemical cells, keeping a permanent magnet behind the working electrode, and the binding process was evaluated by the electrochemical detection of [10]-gingerol. The assay method proposed was also employed to calculate the [10]-gingerol-αVß3 integrin association constant, which was calculated as 4.3 × 107 M-1. The method proposed proved to be a good label-free alternative to ligand-protein interaction studies. Graphical abstract ᅟ.

Development and validation of a bioassay to evaluate binding of adalimumab to cell membrane-anchored TNFα using flow cytometry detection.

Physicochemical and structural properties of proteins used as active pharmaceutical ingredients of biopharmaceuticals are determinant to carry out their biological activity. In this regard, the assays intended to evaluate functionality of biopharmaceuticals provide confirmatory evidence that they contain the appropriate physicochemical properties and structural conformation. The validation of the methodologies used for the assessment of critical quality attributes of biopharmaceuticals is a key requirement for manufacturing under GMP environments. Herein we present the development and validation of a flow cytometry-based methodology for the evaluation of adalimumab's affinity towards membrane-bound TNFα (mTNFα) on recombinant CHO cells. This in vitro methodology measures the interaction between an in-solution antibody and its target molecule onto the cell surface through a fluorescent signal. The characteristics evaluated during the validation exercise showed that this methodology is suitable for its intended purpose. The assay demonstrated to be accurate (r2 = 0.92, slope = 1.20), precise (%CV ≤ 18.31) and specific (curve fitting, r2 = 0.986-0.997) to evaluate binding of adalimumab to mTNFα. The results obtained here provide evidence that detection by flow cytometry is a viable alternative for bioassays used in the pharmaceutical industry. In addition, this methodology could be standardized for the evaluation of other biomolecules acting through the same mechanism of action.

Assessment of new triplet forming artificial nucleobases as RNA ligands directed towards HCV IRES IIId loop.

We report the synthesis of two new artificial nucleobase scaffolds, 1 and 2, featuring adequate hydrogen bonding donors and acceptors for the molecular recognition of U:A and C:G base pairs, respectively. The tethering of these structures to various amino acids and the assessment of these artificial nucleobase-amino acid conjugates as RNA ligands against a model of HCV IRES IIId domain are also reported. Compound 1e displayed the highest affinity (Kd twice lower than neomycin - control). Moreover, it appears that this interaction is enthalpically and entropically favored.

New Horizons on Molecular Pharmacology Applied to Drug Discovery: When Resonance Overcomes Radioligand Binding.

One of the cornerstones of rational drug development is the measurement of molecular parameters derived from ligand-receptor interaction, which guides therapeutic windows definition. Over the last decades, radioligand binding has provided valuable contributions in this field as key method for such purposes. However, its limitations spurred the development of more exquisite techniques for determining such parameters. For instance, safety risks related to radioactivity waste, expensive and controlled disposal of radioisotopes, radiotracer separation-dependence for affinity analysis, and one-site mathematical models-based fitting of data make radioligand binding a suboptimal approach in providing measures of actual affinity conformations from ligands and G proteincoupled receptors (GPCR). Current advances on high-throughput screening (HTS) assays have markedly extended the options of sparing sensitive ways for monitoring ligand affinity. The advent of the novel bioluminescent donor NanoLuc luciferase (Nluc), engineered from Oplophorus gracilirostris luciferase, allowed fitting bioluminescence resonance energy transfer (BRET) for monitoring ligand binding. Such novel approach named Nluc-based BRET (NanoBRET) binding assay consists of a real-time homogeneous proximity assay that overcomes radioligand binding limitations but ensures the quality in affinity measurements. Here, we cover the main advantages of NanoBRET protocol and the undesirable drawbacks of radioligand binding as molecular methods that span pharmacological toolbox applied to Drug Discovery. Also, we provide a novel perspective for the application of NanoBRET technology in affinity assays for multiple-state binding mechanisms involving oligomerization and/or functional biased selectivity. This new angle was proposed based on specific biophysical criteria required for the real-time homogeneity assigned to the proximity NanoBRET protocol.

Production and purification of an untagged recombinant pneumococcal surface protein A (PspA4Pro) with high-purity and low endotoxin content.

Streptococcus pneumoniae is the main cause of pneumonia, meningitis, and other conditions that kill thousands of children every year worldwide. The replacement of pneumococcal serotypes among the vaccinated population has evidenced the need for new vaccines with broader coverage and driven the research for protein-based vaccines. Pneumococcal surface protein A (PspA) protects S. pneumoniae from the bactericidal effect of human apolactoferrin and prevents complement deposition. Several studies indicate that PspA is a very promising target for novel vaccine formulations. Here we describe a production and purification process for an untagged recombinant fragment of PspA from clade 4 (PspA4Pro), which has been shown to be cross-reactive with several PspA variants. PspA4Pro was obtained using lactose as inducer in Phytone auto-induction batch or glycerol limited fed-batch in 5-L bioreactor. The purification process includes two novel steps: (i) clarification using a cationic detergent to precipitate contaminant proteins, nucleic acids, and other negatively charged molecules as the lipopolysaccharide, which is the major endotoxin; and (ii) cryoprecipitation that eliminates aggregates and contaminants, which precipitate at -20 °C and pH 4.0, leaving PspA4Pro in the supernatant. The final process consisted of cell rupture in a continuous high-pressure homogenizer, clarification, anion exchange chromatography, cryoprecipitation, and cation exchange chromatography. This process avoided costly tag removal steps and recovered 35.3 ± 2.5% of PspA4Pro with 97.8 ± 0.36% purity and reduced endotoxin concentration by >99.9%. Circular dichroism and lactoferrin binding assay showed that PspA4Pro secondary structure and biological activity were preserved after purification and remained stable in a wide range of temperatures and pH values.

Angiotensin converting enzyme immobilized on magnetic beads as a tool for ligand fishing.

Angiotensin converting enzyme (ACE) presents an important role in blood pressure regulation, since that converts angiotensin I to the vasoconstrictor angiotensin II. Some commercially available ACE inhibitors are captopril, lisinopril and enalapril; due to their side effects, naturally occurring inhibitors have been prospected. In order to endorse this research field we have developed a new tool for ACE ligand screening. To this end, ACE was extracted from bovine lung, purified and chemically immobilized in modified ferrite magnetic beads (ACE-MBs). The ACE-MBs have shown a Michaelian kinetic behavior towards hippuryl-histidyl-leucine. Moreover, as proof of concept, the ACE-MBs was inhibited by lisinopril with a half maximal inhibitory concentration (IC50) of 10nM. At the fishing assay, ACE-MBs were able not only to fish out the reference inhibitor, but also one peptide from a pool of tryptic digested BSA. In conclusion, ACE-MBs emerge as new straightforward tool for ACE kinetics determination, inhibition and binder screening.

New 2-Aminothiazoline derivatives lower blood pressure of spontaneously hypertensive rats (SHR) via I1-imidazoline and alpha-2 adrenergic receptors activation.

2-Aminothiazolines share an isosteric relationship with imidazolines and oxazolines with antihypertensive activity mainly mediated by the imidazoline I1-receptor. In the present work, we have prepared five aminothiazolines, following a previously described synthetic pathway. Aminothiazolines derived from dicyclopropylmethylamine (ATZ1) and cyclohexylamine (3) are unprecedented in the literature. Competitive radioligand assay was carried out with all synthetic compounds, and the I1 receptor affinity in comparison to rilmenidine in PC12 cells was determined. Surprisingly, the rilmenidine isoster (ATZ1) showed no I1-receptor interaction. Diethyl (ATZ4) and 2-ethyl-hexylamine (ATZ5) derivatives bind to the receptor with 11.98 and 10.94nmol/l, respectively. These compounds were selected for in vivo experiments. Both compounds reduced the blood pressure of spontaneously hypertensive rats (SHR). The hypotensive effect of these compounds was abrogated in the presence of α2 adrenergic (yohimbine) and I1 (efaroxan) receptor antagonists suggesting that both aminothiazolines bind to the adrenergic and imidazoline receptors. Lipinski's descriptors of the synthesized aminothiazolines were calculated and are similar to the known imidazoline I1 receptor ligands. 3D-Similarity between ATZ5 and agmatine, the natural imidazoline receptor ligand, was also observed.

Use of cross-reactivity immunoassay to orient insulin replacement in diabetic patients with high levels of insulin antibodies.

The prevalence and high levels of anti-insulin antibodies (IA) have frequently been associated with brittle diabetes, lipodystrophy in the areas where the insulin is injected and/or poor metabolic control. When this happens the usual criterion adopted is the empirical change of insulin type and/or formulation intending to diminish the IA level and then to decrease the undesirable side-effects. Here, we present a rational two step radiometric method consisting in: A) a first-line radioligand binding assay (RBA) to assess IA in sera of these patients and detecting those with high levels. B) applying a displacement assay (RIA) to determine the in vitro cross-reactivity parameters (affinity constants and selectivity ratios) that quantify the relative degree of interaction between antibodies and alternative insulin analogs. From these results we conclude that conventional criteria for selection of insulin analogs, in terms of pharmacokinetic and pharmacodinamic parameters, should be complemented with an appropriate test to assess affinity parameters when high IA title is demonstrated. •This manuscript introduces a rational method to determine the appropriated insulin replacement when high insulin antibodies levels are present.•This protocol provides instructions and details in mathematical tools and laboratory processes for the analysis of serum samples.•This method proved to be successful in a single case and requires confirmation using a large group of patients.

G-protein activation revealed by [35S]-GTPγS binding assay is involved on the antidepressant-like effect of Hyperi cum caprifoliatum and Hypericum polyanthemumcyclohexane extracts

AbstractPrevious studies by us demonstrated the antidepressant-like and antinociceptive effects of lipophilic extracts and dimeric acyl-phloroglucinols from species of the genus Hypericum native to Southern Brazil. Uliginosin B and HC1 (an enriched phloroglucinol fraction from Hypericum caprifoliatum) are able to inhibit monoamine synaptosomal uptake without binding to the monoaminergic sites on neuronal transporters, unlike classical antidepressants. The current study aimed at investigating the action of H. caprifoliatum Cham. & Schltdl. and Hypericum polyanthemum Klotzsch ex Reichardt, Hypericaceae, cyclohexane extracts and their main component, HC1 and uliginosin B, on G protein coupled receptors by using the [35S]-guanosine-5′-O-(3-thio)triphosphate ([35S]-GTPγS) binding assay, which reveals the G protein activity. The antidepressant-like effect of acute (one or three treatments within 24 h) and repeated (five days with and without a three day wash-out) treatments with the cyclohexane extracts was evaluated using the rat forced swimming test. The [35S]-GTPγS binding to monoamines and opioid receptors stimulated by agonists was performed ex vivo in brain membranes of rats acutely or repeatedly treated with the cyclohexane extracts. The effect of HC1 and Uliginosin B on [35S]-GTPγS binding assay was performed by direct incubation with brain membranes in the absence of agonists. Their antidepressant-like effect was evaluated through the mice forced swimming test. The extracts, HC1 and Uliginosin B showed antidepressant-like effect in the forced swimming test. The acute treatments with extracts increased the [35S]-GTPγS binding stimulated by the monoamines, while after five days of treatment the [35S]-GTPγS binding was reduced even after three day wash-out. These effects are not due to HC1 or Uliginosin B interaction with the receptors, since direct incubation with these phloroglucinols did not affect [35S]-GTPγS binding to membranes. Our findings indicate that H. caprifoliatum and H. polyanthemumextracts bring about adaptive changes in monoamine receptors, which reinforces their antidepressant-like profile.

Utilisation of sperm-binding assay combined with computer-assisted sperm analysis to evaluate frozen-thawed bull semen.

Due to homologies between the chicken egg perivitelline membrane with mammalian zona pellucida proteins, spermatozoa of several species are able to bind to this membrane. However, adequate standardisation is required to attest possible applications of this technique for semen evaluation of a given species. Therefore, we thawed and divided cryopreserved semen samples into two aliquotes, one kept in water bath at 37 °C (thawed) and the other submitted to snap-freezing to damage sperm cells (dead spermatozoa). Aliquotes were mixed into different ratios of thawed:dead cells and analysed for motility, membrane and acrosomal integrity, and mitochondrial activity. In parallel, chicken egg perivitelline membranes were inseminated with these ratios, and the number of spermatozoa bound per mm(2) of membrane was assessed by conventional microscopy (CM) and computer-assisted sperm analysis (CASA). Linear regression showed high correlation between thawed:dead sperm ratio and number of spermatozoa bound to the membrane (CM: r(2) = 0.91 and CASA: r(2) = 0.92 respectively). Additionally, positive correlations were found between the number of spermatozoa bound to the membrane and acrosomal integrity, membrane integrity, mitochondrial activity and motility. These findings indicate that sperm-egg-binding assay associated with CASA is a reliable, practical and inexpensive method for examining the fertilising capacity of cryopreserved bull semen.