An ISFET-based anion sensor for the potentiometric detection of organic acids in liquid chromatography

An ion-selective field effect transistor (ISFET) was applied as a potentiometric detector in liquid chromatography (LC) for the determination of organic acids. The ISFET was prepared by coating the gate insulator of the encapsulated transistor with a poly(vinyl chloride) (PVC) matrix membrane containing methyltridodecylammoniumchloride, which enables the detection of organic anions. The ISFET was tested for its applicability as detector for carboxylic acids in ion-exchange and reversed-phase chromatography. Its analytical characteristics were compared to those of a coated-wire electrode (CWE) and of a conventional type of ion-selective electrode (ISE)

Reaction plate with slidable cover and method to use the same

The invention relates to device for carrying out a reaction, which device comprises a substrate (2) provided with a well (4) for carrying out the reaction, and a cover means (3). According to the invention the cover means (3) is provided with an aperture (5), which in a first position does not overlap the well (4), while in a second position overlapping the well at least partly. Such a device can be filled in a simple manner and evaporation of liquid from the well (4) is to a large extent prevented. The invention also relates to a method for carrying out a reaction in a device according to the inventionApplied Science

Chemical and physical processes for integrated temperature control in microfluidic devices

Microfluidic devices are a promising new tool for studying and optimizing (bio)chemical reactions and analyses. Many (bio)chemical reactions require accurate temperature control, such as for example thermocycling for PCR. Here, a new integrated temperature control system for microfluidic devices is presented, using chemical and physical processes to locally regulate temperature. In demonstration experiments, the evaporation of acetone was used as an endothermic process to cool a microchannel. Additionally, heating of a microchannel was achieved by dissolution of concentrated sulfuric acid in water as an exothermic process. Localization of the contact area of two flows in a microfluidic channel allows control of the position and the magnitude of the thermal effect. © The Royal Society of Chemistry 2003

Determination of the branch location of extra N-acetyllactosamine units in sialo N-linked tetraantennary oligosaccharides

An approach is presented for the determination of the branch location of 1 or 2 extra N-acetyllactosamine units in sialo N-linked carbohydrate chains from glycoproteins. Tetraantennary oligosaccharides containing extra N-acetyllactosamine units were digested with endo-beta-galactosidase, followed by treatment with N-acetyl-beta-glucosaminidase, yielding products which could be analysed by 1H-NMR spectroscopy, thereby giving conclusive data about the location of the extra units in the intact structures

Determination of the branch location of extra N-acetyllactosamine units in sialo N-linked tetraantennary oligosaccharides

An approach is presented for the determination of the branch location of 1 or 2 extra N-acetyllactosamine units in sialo N-linked carbohydrate chains from glycoproteins. Tetraantennary oligosaccharides containing extra N-acetyllactosamine units were digested with endo-beta-galactosidase, followed by treatment with N-acetyl-beta-glucosaminidase, yielding products which could be analysed by 1H-NMR spectroscopy, thereby giving conclusive data about the location of the extra units in the intact structures

Structural analysis of the sialylated N- and O-linked carbohydrate chains of recombinant human erythropoietin expressed in Chinese hamster ovary cells. Sialylation patterns and branch location of dimeric N-acetyllactosamine units

The N-linked carbohydrate chains of recombinant human erythropoietin expressed in CHO cells were quantitatively released with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F, separated from the remaining O-glycoprotein by gel-permeation chromatography, and subsequently fractionated via FPLC on Mono Q, HPLC on Lichrosorb-NH2 and high-pH anion-exchange chromatography on CarboPac PA1. The purified sialylated oligosaccharides were analyzed by one-dimensional and two-dimensional 500-MHz 1H-NMR spectroscopy. When necessary, oligosaccharides were treated with endo-beta-galactosidase (and N-acetyl-beta-glucosaminidase) followed by 1H-NMR analysis of the incubation products, to obtain additional structural information. Di-, tri-, tri'- and tetraantennary, N-acetyllactosamine-type oligosaccharides occur which can be completely (major) or partially (minor) sialylated. Three different types of alpha2-3-linked sialic acids are present, namely, N-acetylneuraminic acid (95%), N-glycolylneuraminic acid (2%) and N-acetyl-9-O-acetylneuraminic acid (3%). In the case of partial sialylation, a non-random distribution of the sialic acids over the branches is observed. One or two extra N-acetyllactosamine units, being exclusively located in the branches attached to the alpha1-6-linked Man residue, can be present in completely or partially sialylated di-, tri'-, and tetraantennary oligosaccharides. Tetraantennary oligosaccharides with, N-acetyllactosamine repeats could be digested quantitatively with endo-beta-galactosidase from Bacteroides fragilis, whereas under the same conditions tri'antennary oligosaccharides Hardly reacted ( 75%). The O-linked carbohydrate chains were released from the O-glycoprotein by alkaline borohydride treatment, and purified via FPLC on Mono Q and HPLC on Lichrosorb-NH2. Two O-glycans were found, namely, Neu5Acalpha2-3Galbeta1-3GalNAc-ol and Neu5Acalpha2-3Galbeta1-3(Neu5 Ac2-6)GalNAc-ol

Structure determination of the major N- and O-linked carbohydrate chains of the β subunit from equine chorionic gonadotropin

The carbohydrate moieties of equine chorionic gonadotropin α and β subunits were released from the protein backbones by successive treatments with peptide-(N-acetyl-β-glucosaminyl)asparagine amidase F and alkaline borohydride and then fractionated by FPLC and HPLC. The major N- and O-linked glycans of the β subunit were characterized by 500-MHz 1H-NMR spectroscopy, showing a remarkable structural heterogeneity for the N-glycosidically linked chains, comprising mono-,di-, tri- and tri'-antennary N-acetyllactosamine type of glycans, being partly α1-6 fucosylated at the Asn-bound GlcNAc residue and having α2-6 and α2-3 linked N-acetyl- and N-acetyl-4-O-acetylneuraminic acid residues as sialic acid constituents. Significant differences in this respect were detected for the partially characterized glycans of the α subunit. The major part of the O-linked carbohydrate chains, occurring solely in the β subunit, is formed by tri-, tetra-, penta- and hexa-saccharides. There are indications for the presence of oligo(N-acetyllactosamine) units in both the N- and O-linked glycans of the β subunit