Loop Protein Engineering for Improved Transglycosylation Activity of a β‐N‐Acetylhexosaminidase

Certain enzymes of the glycoside hydrolase family 20 (GH20) exert transglycosylation activity and catalyze the transfer of β‐N‐acetylglucosamine (GlcNAc) from a chitobiose donor to lactose to produce lacto‐N‐triose II (LNT2), a key human milk oligosaccharide backbone moiety. The present work is aimed at increasing the transglycosylation activity of two selected hexosaminidases, HEX1 and HEX2, to synthesize LNT2 from lactose and chitobiose. Peptide pattern recognition analysis was used to categorize all GH20 proteins in subgroups. On this basis, we identified a series of proteins related to HEX1 and HEX2. By sequence alignment, four additional loop sequences were identified that were not present in HEX1 and HEX2. Insertion of these loop sequences into the wild‐type sequences induced increased transglycosylation activity for three out of eight mutants. The best mutant, HEX1_GTEPG, had a transglycosylation yield of LNT2 on the donor that was nine times higher than that of the wild‐type enzyme. Homology modeling of the enzymes revealed that the loop insertion produced a more shielded substrate‐binding pocket. This shielding is suggested to explain the reduced hydrolytic activity, which in turn resulted in the increased transglycosylation activity of HEX1_GTEPG.     

On the design of filters for fourier and oSVD-based deconvolution in bolus tracking perfusion MRI

Object  

Bolus tracking perfusion evaluation relies on the deconvolution of a tracers concentration time-courses in an arterial and a tissue voxel following the tracer kinetic model. The object of this work is to propose a method to design a data-driven Tikhonov regularization filter in the Fourier domain and to compare it to the singular value decomposition (SVD)–based approaches using the mathematical equivalence of Fourier and circular SVD (oSVD).     

Prediction of limits of lubrication in strip reduction testing

Pick-up and galling due to lubricant film breakdown is a severe limitation in cold forming of tribologically difficult metals like stainless steel and aluminium. The present paper describes a method of combined experimental and numerical analysis to quantify the limits of lubrication in a dedicated simulative strip reduction test. The limit of lubrication is quantified as the threshold drawing length before galling occurs. A numerical model of the test is established calculating tool/work piece interface temperatures and normal pressures. Identifying a critical maximum value of the interface temperature the results show good agreement between numerically predicted and experimentally observed threshold drawing lengths at different test conditions.     

Artefact reduction with alternative cuff configurations

In nerve cuff electrode recordings of neural signals, the pick-up of interfering signals can be reduced by choosing appropriate cuff configurations. In the traditionally used tripolar configuration, short circuiting of the end electrodes is expected to reduce the field inside the cuff from interfering signals. A model study suggests that moving the end electrodes toward the center of the cuff reduces the pick-up of interfering signals. In this paper, these properties are studied in more detail using a rabbit model. In addition, a new cuff configuration is suggested, which has an additional set of short circuited end electrodes. The total improvement of signal-to-noise ratio in the new configuration as compared with the traditionally used tripolar configuration was 73% for muscle signals and 127% for the stimulus pulse.     

Pharmacokinetics of diazepam in disordered liver function

The occurrence of spontaneous abortions in women, working in all branches of industry, were studied. 5 frequencies of abortion were determined in regard to the professional employment of the subject. The highest frequency was encountered in women working in the chemical industry, such as in pharmaceutical industries, light and heavy metallurgy, plastics, and the railway industry. The lowest frequency was found in those employed in offices. There is an obvious correlation between the level of stress and the rate of spontaneous abortions. The high rate of abortions revealed in the indicated industries lead to recommendations for more detailed studies of professional and other factors.     

Occupational exposures and health among Danish farmers working in swine confinement buildings

In a cross-sectional study at 11 large pig-breeding farms various work-related exposures were measured. The purpose was to record several simultaneous exposures in relation to various work tasks. The concentration of total dust and respirable dust was 4.13 mg/m³ and 0.48 mg/m³ respectively. For all farmers the relative heart rate increase during work was 29% of maximal work capacity (±9.7%), indicating a high work load. Increased pulmonary ventilation causes a higher risk for deposition of dust in the airways. The total tonnage lifted per day was 4,725 kg and was considered to be high according to Danish guidelines. During 40% of the working time, the work was performed with a forward flexion of the back of more than 20°. The load on the back may be the cause of the high one-year prevalence of low back pain at 62%. The work task of feeding pigs was the task with the highest number of simultaneous exposures.