Determination of telmisartan in human blood plasma: Part I: Immunoassay development

Telmisartan is an angiotensin II receptor antagonist and a known drug against high blood pressure. In this report, the development of a new and rapid analytical technique, an enzyme-linked immunosorbent assay (ELISA) for the determination of telmisartan in human blood plasma is described. The immunoassay is based on a conversion of 4-(N-methylhydrazino)-7-nitro-2,1,3-benzooxadiazole (MNBDH) to 4-(N-methylamino)-7-nitro-2,1,3-benzooxadiazole (MNBDA), which is detected by fluorescence spectroscopy. The limit of detection was 0.1 ng/mL, the limit of quantification was 0.3 ng/mL and the working range extended from 0.3 ng/mL to 300 ng/mL.     

Stereospecific cyclodehydration of 1,4-sulfanylalcohols to thiolanes: mechanistic insights

A series of thiolanes were prepared by cyclodehydration of sulfanylalcohols in the presence of catalytic amounts of p-toluenesulfonic acid or by using K10 clay. The sulfur heterocycles were synthesised in good to excellent yields using either a conventional Dean-Stark method or microwave irradiation under solvent-free conditions. The reaction could be performed regio- and stereoselectively and its mechanism was investigated by means of enantio- and diastereomerically enriched substrates. In contrast to previous studies, our results are consistent with an intramolecular S_N2-type mechanism as a general pathway.     

A molecular tool kit for the variable design of logic operations (NOR, INH, EnNOR)

A simple set of five components was used to design molecular logic gates based on phthalimide-sensitised Tb(III) luminescence, including the first report of an enabled NOR (EnNOR) gate.     

Sensor Array Based Determination of Edman Degradated Amino Acids Using Poly(p-phenyleneethynylene)s

A cross-reactive optical sensor array based on poly(p-phenyleneethynylene)s (PPEs) determines Edman degraded amino acids. We report a sensor array composed of three anionic PPEs P1–P3 , and their electrostatic complexes with metal ions (Fe²⁺, Cu²⁺, Co²⁺). We recorded distinct fluorescence intensity response patterns as “fingerprints” of this chemical tongue toward standard phenylthiohydantoin (PTH) amino acids—degradation products of the Edman process. These “fingerprints” were converted into canonical scores by linear discrimination analysis (LDA), which differentiates all of the PTH-amino acids. This array discriminates PTH-amino acid residues degraded from an oligopeptide through Edman sequencing. This approach is complementary to chromatography approaches which rely on mass spectrometry; our array offers the advantage of simplicity.     

Visible Light-Gated Organocatalysis Using a RuII-Photocage

The light-gated organocatalysis via the release of 4-N,N-dimethylaminopyridine (DMAP) by irradiation of the [Ru(bpy)₂(DMAP)₂]²⁺ complex with visible light was investigated. As model reaction the acetylation of benzyl alcohols with acetic anhydride was chosen. The pre-catalyst releases one DMAP molecule on irradiation at wavelengths longer than 455 nm. The photochemical process was characterized by steady-state irradiation and ultrafast transient absorption spectroscopy. The latter enabled the observation of the ³MLCT state and the spectral features of the penta-coordinated intermediate [Ru(bpy)₂(DMAP)]²⁺. The released DMAP catalyzes the acetylation of a wide range of benzyl alcohols with chemical yields of up to 99 %. Control experiments revealed unequivocally that it is the released DMAP which takes the role of the catalyst.     

Aldehyde cruciforms: dosimeters for primary and secondary amines

We demonstrate that aldehyde-substituted donor-acceptor cruciforms [1,4-bis(arylethynyl)-2,5-distyrylbenzenes] are useful dosimeters for primary amines, primary diamines, and secondary amines. The 1,n-diamines are particularly reactive towards this dosimeter and can be detected in less than 100 ppm concentration. Using a single aldehyde-functionalized cruciform in seven different solvents allowed us to discern fourteen different amines by digital photography and statistical evaluation of the response patterns extracted as red, green, blue (RGB) values.     

Single channel recordings of alpha-hemolysin reconstituted in S-layer-supported lipid bilayers.

Previous studies demonstrated that lipid membranes attached to a proteinaceous crystalline surface-layer (S-layer) revealed a prolonged lifetime and showed a reduced tendency to rupture in the presence of membrane active molecules. In addition, comparative studies on folded and S-layer-supported lipid membranes (SsLM) revealed an uniform capacitance of 0.64 +/- 0.04 microF/cm(2) for both composite membranes. In the present study, the feasibility to reconstitute the channel-forming protein alpha-hemolysin (alpha HL) into SsLM at single channel resolution was investigated. Single alpha HL channels could be recorded and the intrinsic properties like unitary conductance, current-voltage characteristics, and closure was found to be similar at both membranes. Thus, the tightly attached S-layer allowed complete reconstitution of alpha HL channels in SsLM.     

RbCrIII(C2O4)2·2H2O,Cs2Mg(C2O4)2·4H2O and Rb2CuII(C2O4)2·2H2O: three new complex oxalate hydrates

Rubidium chromium(III) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­chromium(III)­rubidium(I)], [RbCr(C₂O₄)₂(H₂O)₂], (I), and dicaesium magnesium dioxalate tetrahydrate [tetra­aqua­bis(μ‐oxalato)­magnesium(II)­dicaesium(I)], [Cs₂Mg(C₂­O₄)₂(H₂O)₄], (II), have layered structures which are new among double‐metal oxalates. In (I), the Rb and Cr atoms lie on sites with imposed 2/m symmetry and the unique water molecule lies on a mirror plane; in (II), the Mg atom lies on a twofold axis. The two non‐equivalent Cr and Mg atoms both show octahedral coordination, with a mean Cr—O distance of 1.966 Å and a mean Mg—O distance of 2.066 Å. Dirubid­ium copper(II) dioxalate dihydrate [di­aqua­bis(μ‐oxalato)­copper(II)­dirubidium(I)], [Rb₂Cu(C₂O₄)₂(H₂O)₂], (III), is also layered and is isotypic with the previously described K₂‐ and (NH₄)₂Cu^II(C₂O₄)₂·2H₂O compounds. The two non‐equivalent Cu atoms lie on inversion centres and are both (4+2)‐coordinated. Hydro­gen bonds are medium‐strong to weak in the three compounds. The oxalate groups are slightly non‐planar only in the Cs–Mg compound, (II), and are more distinctly non‐planar in the K–Cu compound, (III).