17β-Estradiol residues and estrogenic activities in the Hawkesbury River, Australia.

Two highly sensitive ELISAs for the specific detection of 17β-estradiol (E2) residues were developed, showing the limits of detection (LOD, a concentration at 15% inhibition of color development) of 0.04 ± 0.02 μg/L and 0.

A survey of 17α-ethinylestradiol and mestranol residues in Hawkesbury River, Australia, using a highly specific enzyme-linked immunosorbent assay (ELISA) demonstrates the levels of potential biological significance.

This study reports on the potential status of 17α-ethinylestradiol (EE2) and mestranol (MeEE2) residues in aquatic environments in New South Wales (NSW), Australia, based on the analysis by a specific ELISA we developed. Polyclonal antibodies were raised against the EE2 hapten with a linker attached at the C3-position to direct the antibody binding towards the ring D of EE2/MeEE2. Using this approach, an ELISA highly specific to EE2 and MeEE2 was successfully developed, showing less than 3.

Γ-aminobutyric acid(C) (GABAC) selective antagonists derived from the bioisosteric modification of 4-aminocyclopent-1-enecarboxylic acid: amides and hydroxamates.

Series of compounds were generated via the bioisosteric replacement of the carboxylate of 4-ACPCA (2) with hydroxamate or amide groups. All compounds from this study exhibited increased selectivity for GABAC, the most potent being 4-ACPHA (10a, IC50 = 13 μM) and 4-ACPAM (11a, IC50 = 10 μM). This provides evidence that a zwitterionic structure is not essential for GABAC antagonists, rather the emphasis lies in appropriate heteroatoms to participate in hydrogen bonding.

Structurally diverse GABA antagonists interact differently with open and closed conformational states of the ρ1 receptor.

Ligands acting on receptors are considered to induce a conformational change within the ligand-binding site by interacting with specific amino acids. In this study, tyrosine 102 (Y102) located in the GABA binding site of the ρ(1) subunit of the GABA(C) receptor was mutated to alanine (ρ(1Y102A)), serine (ρ(1Y102S)), and cysteine (ρ(1Y102C)) to assess the role of this amino acid in the action of 12 known and 2 novel antagonists. Of the mutated receptors, ρ(1Y102S) was constitutively active, providing an opportunity to assess the activity of antagonists on ρ(1) receptors with a proportion of receptors existing in the open conformational state compared to those existing predominantly in the closed conformational state.

GABA analogues derived from 4-aminocyclopent-1-enecarboxylic acid.

The incorporation of extra binding groups onto known ligands is a powerful tool for the development of more potent and selective agents at target sites such as the GABA receptors. In the present work we have attempted to build on the activity of the know potent GABA(A) agonist 4-ACP-3-CA and its cis and trans saturated analogues CACP and TACP. We have investigated reactions to add thiol substituents to the alpha,beta-unsaturated system of 4-ACP-3-CA.

Guanidino acids act as rho1 GABA(C) receptor antagonists.

GABA(C) receptors play a role in myopia, memory-related disorders and circadian rhythms signifying a need to develop potent and selective agents for this class of receptors. Guanidino analogs related to glycine, beta-alanine and taurine were evaluated at human rho(1)GABA(C) receptors expressed in Xenopus oocytes using 2-electrode voltage clamp methods. Of the 12 analogs tested, 8 analogs were active as antagonists and the remaining were inactive.

3-hydroxypyridazine 1-oxides as carboxylate bioisosteres: a new series of subtype-selective AMPA receptor agonists.

Three positional isomers (compounds 1, 2, and 3) of 1-uracilylalanine (willardiine) based on a 3-hydroxypyridazine 1-oxide scaffold with an alanine side-chain at positions 4 (1), 5 (2) or 6 (3) were tested for binding to recombinant homomeric AMPA receptor (AMPA-R) subtypes GluR1-4, as well for excitatory activity on the rat cortical wedge preparation. 1 had approximately 30 times higher affinity than willardiine while showing a similar selectivity profile, i.e.

Synthesis and in vivo evaluation of a novel peripheral benzodiazepine receptor PET radioligand.

The novel pyrazolopyrimidine ligand, N,N-diethyl-2-[2-(4-methoxyphenyl)-5,7-dimethyl-pyrazolo[1,5-a]pyrimidin-3-yl]-acetamide 1 (DPA-713), has been reported as a potent ligand for the peripheral benzodiazepine receptor (PBR) displaying an affinity of K(i)=4.7 nM. In this study, 1 was successfully synthesised and demethylated to form the phenolic derivative 6 as precursor for labelling with carbon-11 (t(1/2) = 20.

Studies on pyridazine azide cyclisation reactions.

Reaction of sodium azide with 4-methyl-3,5,6-tribromopyridazine results in the formation of 3,5,6-triazide intermediate which could cyclise to give two possible bicyclic products while ab initio calculations show that the formation of a tricyclic compound is extremely energetically unfavourable. However, experimentally, only one major product is isolated. The structure of this unstable product has been conclusively established by X-ray crystallography as 3,5-diazido-4-methyl[1,5-b]tetrazolopyridazine confirming theoretical predictions.

A rapid aflatoxin B1 ELISA: development and validation with reduced matrix effects for peanuts, corn, pistachio, and Soybeans.

Among the competitive ELISAs for aflatoxins that have been described, few have been adequately validated for reduced matrix effects. Using an aflatoxin B(1) (AFB(1))-specific polyclonal antibody (produced from AFB(1)-oxime conjugated to bovine serum albumin (BSA)) and AFB(1)- and AFB(2)-enzyme conjugates, four direct competitive ELISAs based on 96-microwell plates (two standard assays and two rapid assays) were developed, paying special attention to producing a robust assay relatively free of interferences for a range of agricultural products. The antibody was AFB(1)-specific, detecting only AFB(1) in a mixture of four aflatoxins (AFB(1), AFB(2), AFG(1), and AFG(2)), but showed significant cross-reaction with AFG(1) (57-61%) when an individual compound was tested.

Rapid enzyme immunoassays for the detection of carbaryl and methoprene in grains.

In order for grain handlers and traders to reliably estimate residues of grain protectants in the field, antibody-based rapid tests were developed for carbaryl (1-naphthyl methylcarbamate) and methoprene [isopropyl (E,E)-(RS)-11-methoxy-3,7,11-trimethyldodeca-2,4-dienoate]. To complement the rapid analysis, a simple and rapid extraction technique was developed. In these tests, a pesticide-containing methanol extract of the grain sample and an enzyme-labeled component are added to precoated strips.