Henrik Chresten Pedersen

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.

Optical waveguide sensor for on-line monitoring of bacteria

A grating-coupled planar optical waveguide sensor is presented for sensing of bacteria by evanescent waves. The waveguide design results in increased depth of penetration into the sample volume, which makes it suitable for detecting micrometer-sized biological objects. We tested the sensors performance by monitoring the adhesion of Escherichia coli K12 cells to the sensor surface.

Monitoring of living cell attachment and spreading using reverse symmetry waveguide sensing

The effect of the attachment and spreading of living cells on the modes of a grating coupled reverse symmetry waveguide sensor is investigated in real time. The reverse symmetry design has an increased probing depth into the sample making it well suited for the monitoring of cell morphology. As a result, significant changes in the incoupling peak height and peak shape were observed during cell attachment and spreading. It is suggested that the area under the incoupling peaks reflects the initial cell attachment process, while the mean peak position is mostly governed by the spreading of the cells.

The influence of nitrogen sources on the α-amylase productivity of Aspergillus oryzae in continuous cultures

Abstract The influence of the nitrogen source on the α-amylase productivity of Aspergillus oryzae was quantified in continuous cultivations. Both inorganic and complex nitrogen sources were investigated and glucose was used as the carbon and energy sources. For production of α-amylase, nitrate was shown to be inferior to ammonia as a nitrogen source. A mixture of ammonia and complex nitrogen sources, such as yeast extract or casein hydrolysate, was better than with ammonia as the sole nitrogen source. Even a low concentration of casein hydrolysate (0.05 g l−1) resulted in a 35% increase in the α-amylase productivity. The higher α-amylase productivity during growth on casein hydrolysate was not caused by increased transcription of the α-amylase genes but was caused by a faster secretion of α-amylase or by a lower binding of α-amylase to the biomass.

Demonstration of reverse symmetry waveguide sensing in aqueous solutions

A reverse symmetry waveguide is presented for evanescent wave sensing in aqueous solutions. The waveguide consists of a thin polystyrene film, supported by a thicker substrate layer of nanoporous silica on glass. The nanoporous substrate layer has a refractive index of nS=1.193, hence, with an aqueous cover refractive index of nC=1.331, a reverse symmetry (nS<nC) is obtained. A surface relief grating formed in the polystyrene film is used as a coupling element. Sensitivities considerably higher than for a conventional waveguide sensor are demonstrated.

Multidepth screening of living cells using optical waveguides.

The use of planar optical waveguides as substrata for label-free, non-invasive monitoring of cells growing on them is demonstrated. Different submicrometre depths (measured from and perpendicular to the substratum surface) can be selected for monitoring. The so-called symmetry waveguide configuration with a low refractive index waveguide support (nanoporous silica with refractive index approximately 1.2) and a polystyrene waveguiding film with a heat-embossed grating coupler is exploited to obtain practically useful differences between the penetration depths of different waveguide modes. Robust data processing techniques are developed to obtain quantitative information about the cell refractive index profile perpendicular to the substratum from the measured effective refractive indices of the modes. In particular, a method is introduced with which cell refractive index variations above and below a predefined and tunable depth can be separated using two modes. The technique can be extended to more modes to gain even more comprehensive information from predefined submicrometre slices of the cell layer. The introduced methods are also suitable for monitoring the kinetics of changes in cell refractive index profiles.

High resolution three‐dimensional cardiac perfusion imaging using compartment‐based k‐t principal component analysis

Three‐dimensional myocardial perfusion imaging requires significant acceleration of data acquisition to achieve whole‐heart coverage with adequate spatial and temporal resolution. The present article introduces a compartment‐based k‐t principal component analysis reconstruction approach, which permits three‐dimensional perfusion imaging at 10‐fold nominal acceleration. Using numerical simulations, it is shown that the compartment‐based method results in accurate representations of dynamic signal intensity changes with significant improvements of temporal fidelity in comparison to conventional k‐t principal component analysis reconstructions. Comparison of the two methods based on rest and stress three‐dimensional perfusion data acquired with 2.3 × 2.3 × 10 mm3 during a 225 msec acquisition window in patients confirms the findings and demonstrates the potential of compartment‐based k‐t principal component analysis for highly accelerated three‐dimensional perfusion imaging. Magn Reson Med, 2011.

Glucoamylase production in batch, chemostat and fed-batch cultivations by an industrial strain of Aspergillus niger

Abstract The Aspergillus niger strain BO-1 was grown in batch, continuous (chemostat) and fed-batch cultivations in order to study the production of the extracellular enzyme glucoamylase under different growth conditions. In the pH range 2.5–6.0, the specific glucoamylase productivity and the specific growth rate of the fungus were independent of pH when grown in batch cultivations. The specific glucoamylase producivity increased linearly with the specific growth rate in the range 0–0.1 h−1 and was constant in the range 0.1–0.2 h−1. Maltose and maltodextrin were non-inducing carbon sources compared to glucose, and the maximum specific growth rate was 0.19 ± 0.02 h−1 irrespective of whether glucose or maltose was the carbon source. In fed-batch cultivations, glucoamylase titres of up to 6.5 g l−1 were obtained even though the strain contained only one copy of the glaA gene.

Cloning and characterization of oah, the gene encoding oxaloacetate hydrolase in Aspergillus niger.

Abstract The enzyme oxaloacetate hydrolase (EC 3.7.1.1), which is involved in oxalate formation, was purified from Aspergillus niger. The native enzyme has a molecular mass of 360–440 kDa, and the denatured enzyme has a molecular mass of 39 kDa, as determined by gel electrophoresis. Enzyme activity is maximal at pH 7.0 and 45 °C. The fraction containing the enzyme activity contained at least five proteins. The N-terminal amino acid sequences of four of these proteins were determined. The amino acid sequences were aligned with EST sequences from A. niger, and an EST sequence that showed 100% identity to all four sequences was identified. Using this EST sequence the gene encoding oxaloacetate hydrolase (oah) was cloned by inverse PCR. It consists of an ORF of 1227 bp with two introns of 92 and 112 bp, respectively. The gene encodes a protein of 341 amino acids with a molecular mass of 37 kDa. Under the growth conditions tested, the highest oah expression was found for growth on acetate as carbon source. The gene was expressed only at pH values higher than 4.0.

Fabrication of reverse symmetry polymer waveguide sensor chips on nanoporous substrates using dip-floating

Reverse symmetry waveguide biosensors employ substrates with a refractive index less than the analyzed aqueous cover sample (1.33). This design offers higher sensitivities for detecting micron scale biological objects such as bacteria and living cells. In the present paper, the fabrication details of reverse symmetry polymer waveguide sensors using nanoporous silica substrates with refractive index 1.2 are presented. Using nanoporous substrates the direct spin-coating deposition of polymer films is not feasible, since the solvent used to dissolve the polymer fills up the nanopores leading to a substrate RI more than 1.33. Instead, a technique—referred to as dip-floating—was applied to create freely floating 150-nm thick polymer films on the surface of water. The films were transferred to the nanoporous substrates simply by pressing the substrates through the air-floating film–water interface. A heat molding technique using a PDMS grating was used to create integrated gratings on the polymer films for light coupling.