Christian Pedersen

Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Monosaccharides

Publisher Summary This chapter provides an overview of the 13 Carbon-nuclear magnetic resonance ( 13 C-NMR) spectroscopy of monosaccharides. The 13 C-NMR spectroscopy has become increasingly important as a tool for the characterization and structural elucidation of sugars and their derivatives. Although 13 C-NMR is closely related to 1 H-NMR spectroscopy, especially when both types of spectra are recorded with Fourier-transform instruments, the two techniques are sufficiently different to be valuable complements to each other. In many cases, in particular when dealing with complex molecules such as polysaccharides, the amount of information obtainable from 1 H-NMR spectra is limited as compared to that revealed by 13 C- NMR spectra. This chapter provides an almost complete collection of 13 C- NMR chemical shifts of monosaccharides, their methyl glycosides, and acetates, along with the examples of shift data for as many different types of monosaccharide derivative as possible. It also provides details on sampling techniques and assignment techniques, and discusses the identity of monosaccharides, their structure determination, and conformational analysis .

Carbon-13 Nuclear Magnetic Resonance Data for Oligosaccharides

Publisher Summary This chapter presents a compilation of 13 C-nuclear magnetic resonance (NMR) data for oligosaccharides in the form of tables. The literature-survey presented in the chapter covers most of the data of 1982, and all of the information given had been measured for solutions in D 2 O unless stated otherwise. The data for peracetates of xylobioses and of glucobioses were recorded for solutions in CDCl 3 . All data have been copied from the original articles. For mutarotated mixtures of trisaccharides and larger oligosaccharides, the complete set of data is given for the α anomer, but only the chemical shifts for the reducing end of the anomer are given, provided that all other chemical shifts (for the remaining units) are identical. The sampling and assignment techniques used for the measurement of 13 C-NMR spectra of oligosaccharides are identical to those for monosaccharides. Particularly for oligosaccharides, it is important to measure the spectra at the same temperature—that is, with a precision better than ±0.5 p.p.m., when data are to be compared accurately.

A study of 13CH coupling constants in hexopyranoses

Proton decoupled and undecoupled 13C n.m.r. spectra have been measured on a number of hexopyranoses. The direct coupling constants between the anomeric carbon atoms and protons {1J[13C–H(1)]} were found to be ca. 160 in the β-anomers and ca. 170 Hz in the α-anomers; the difference of ca. 10 Hz between pairs of anomers was found in almost all cases. Chemical shifts and 1J(13CH) values of the other carbon atoms in the pyranose rings were also measured.

The behaviour of d-fructose and inulin towards anhydrous hydrogen fluoride☆

Abstract Inulin and d -fructose are quantitatively converted into a mixture of d -fructose dianhydrides on treatment with anhydrous hydrogen fluoride. Of the six dianhydrides isolated, five are known compounds, whereas one, β- d -fructofuranose β- d -fructopyranose 2,1′:3,2′-dianhydride, has not been described hitherto. The structures of two of the known dianhydrides have been revised. The relative amounts of dianhydrides obtained depend on the reaction conditions. The reaction of d -fructose with hydrogen fluoride is shown, using 13 C-n.m.r. spectroscopy, to involve d -fructofuranosyl fluoride as a probable intermediate. Dianhydrides are also formed when d -fructose is treated with methanol and sulfuric acid under Fischer glycosidation conditions or with trifluoroacetic acid.

The behavior of chitin towards anhydrous hydrogen fluoride. Preparation of β-(1→4)-linked 2-acetamido-2-deoxy-d-glucopyranosyl oligosaccharides☆

Abstract Fluorohydrolysis of chitin in anhydrous hydrogen fluoride led to β-(1→4)-linked 2-acetamido-2-deoxy- d -glucopyranosyl oligosaccharides in almost quantitative yield. The average d.p. depended on both reaction time and temperature, and was conveniently monitored by 13 C-n.m.r. spectroscopy and gel-exclusion chromatography. Preparative fractionation of oligosaccharides of chitin (d.p. 2–10) was conveniently achieved by gel-exclusion chromatography in Bio-Gel P-4.

Tunable high-power narrow-linewidth semiconductor laser based on an external-cavity tapered amplifier

A high-power narrow-linewidth laser system based on a tapered semiconductor optical amplifier in external cavity is demonstrated. The external cavity laser system uses a new tapered amplifier with a super-large optical-cavity (SLOC) design that leads to improved performance of the external cavity diode lasers. The laser system is tunable over a 29 nm range centered at 802 nm. As high as 1.95 W output power is obtained at 803.84 nm, and an output power above 1.5 W is achieved from 793 to 812 nm at operating current of 3.0 A. The emission linewidth is below 0.004 nm and the beam quality factor M2 is below 1.3 over the 29 nm tunable range. As an example of application, the laser system is used as a pump source for the generation of 405 nm blue light by single-pass frequency doubling in a periodically poled KTiOPO4. An output power of 24 mW at 405 nm, corresponding to a conversion efficiency of 0.83%/W is attained.

Preparation of some bromodeoxyaldonic acids

Abstract Reaction of L -ascorbic acid with hydrogen bromide in acetic acid gave 6-bromo-6-deoxy- L -ascorbic acid, which was converted into 5,6-dideoxy- D - glycero -hex-2,3-enono-1,4-lactone. Hexonic acids or their lactones also gave bromo compounds on treatment with HBrAcOH. From D -galactono-1,4-lactone a 6-bromo derivative was obtained. Calcium D -gluconate yielded 2,6-dibromo-2,6-dideoxy- D -mannono-1,4-lactone, whereas D -mannono-1,4-lactone gave 2,6-dibromo-2,6-dideoxy- D -glucono-1,4-lactone.

PCR biocompatibility of Lab-on-a-chip and MEMS materials

DNA amplification using the polymerase chain reaction (PCR) is an important tool in biotechnology, pathogen surveillance in food, medical and forensic science etc. The PCR technique is now an important part of the research in and development of miniaturized biochemical analysis systems. However, reduced or no DNA amplification at all is an important challenge for microfabricated PCR devices due to a negative interaction between PCR chemicals and the surrounding environment, i.e. the materials encapsulating the PCR mix. Materials of special interest regarding PCR compatibility are silicon, glass and polymers, which are important in the fabrication of microelectromechanical systems (MEMS), micro total analysis systems (µTAS) and lab-on-a-chip (LOC) systems. The PCR inhibition effect is a particularly important phenomenon in microsystems due to an increased surface-to-volume ratio which enhances the possibility of interaction between the surfaces and ingredients in the PCR mixture. By proper surface treatment the PCR reaction can be facilitated and in this paper we present a systematic and quantitative study of the impact on the PCR compatibility of a chemical and a biological surface treatment. The chemical treatments are based on the silanizing agent dichlordimethylsilane [(CH3)2SiCl2]], while the biological treatment is based on the protein bovine serum albumin (BSA). We present a simple model system for the investigation of the PCR compatibility of three widely used materials in microfabrication, namely silicon, glass and SU-8. The impact on PCR performance, measured by means of PCR efficiency, of untreated as well as chemically and biologically treated materials is studied. We show a convenient method of assessing the PCR compatibility of silicon, glass and SU-8 with a degree of information not presented before.

Fourier domain mode-locked swept source at 1050 nm based on a tapered amplifier

While swept source optical coherence tomography (OCT) in the 1050 nm range is promising for retinal imaging, there are certain challenges. Conventional semiconductor gain media have limited output power, and the performance of high-speed Fourier domain mode-locked (FDML) lasers suffers from chromatic dispersion in standard optical fiber. We developed a novel light source with a tapered amplifier as gain medium, and investigated the FDML performance comparing two fiber delay lines with different dispersion properties. We introduced an additional gain element into the resonator, and thereby achieved stable FDML operation, exploiting the full bandwidth of the tapered amplifier despite high dispersion. The light source operates at a repetition rate of 116 kHz with an effective average output power in excess of 30 mW. With a total sweep range of 70 nm, we achieved an axial resolution of 15 microm in air (approximately 11 microm in tissue) in OCT measurements. As our work shows, tapered amplifiers are suitable gain media for swept sources at 1050 nm with increased output power, while high gain counteracts dispersion effects in an FDML laser.

The preparation of some bromodeoxy- and deoxy-hexoses from bromodeoxyaldonic acids☆

Abstract The reduction of 2,6-dibromo-2,6-dideoxy- D -mannono- and 2,6-dibromo-2,6-dideoxy- D -glucono-1,4-lactone with sodium borohydride affords 2,6-dibromo-2,6-dideoxy- D -mannose and 2,6-dibromo-2,6-dideoxy- D -glucose, respectively, which may be isolated as their acetates. Similarly, 2-bromo-2,6-dideoxy- L- -glucono-1,4-lactone yields 2-bromo-2,6-dideoxy- L -glucose. Hydrogenolysis of 2,6-dibromo-2,6-dideoxy- D -mannono-1,4-lactone gives 6-bromo-2,6-dideoxy- D - arabino -hexono-1,4-lactone and, subsequently, 2,6-dideoxy- D - arabino -hexono-1,4-lactone. Reduction of the latter with bis(1,2-dimethylpropyl)borane leads to 2,6-dideoxy- D - arabino -hexose, which may be converted into methyl 2,6-dideoxy-3,4-di- O - p -nitrobenzoyl- D - arabino -hexopyranoside.