Interplay of Trans- and Cis-Interactions of Glycolipids in Membrane Adhesion

Glycolipids mediate stable membrane adhesion of potential biological relevance. In this article, we investigate the trans- and cis-interactions of glycolipids in molecular dynamics simulations and relate these interactions to the glycolipid-induced average separations of membranes obtained from neutron scattering experiments. We find that the cis-interactions between glycolipids in the same membrane leaflet tend to strengthen the trans-interactions between glycolipids in apposing leaflets. The trans-interactions of the glycolipids in our simulations require local membrane separations that are significantly smaller than the average membrane separations in the neutron scattering experiments, which indicates an important role of membrane shape fluctuations in glycolipid trans-binding. Simulations at the experimentally measured average membrane separations provide a molecular picture of the interplay between glycolipid attraction and steric repulsion of the fluctuating membranes probed in the experiments

Concept For Fast Spectral Characterisation Of Imaging Spectrometers

For imaging spectrometers in the range of 350 - 2500 nm spectral characterization is accomplished currently at the Calibration Home Base (CHB) facility at DLR Oberpfaffenhofen using a Quartz-Tungsten-Halogen (QTH) lamp and a monochromator illuminating one pixel at a time. Here a new concept of spectral measurements is presented by making use of a laser driven optical parametric oscillator (OPO) tunable through the spectral region of 405 nm to 2550 nm allowing to characterize all of the pixels simultaneously. The advantages as speed of measurement due to higher spectral radiance, easier alignment and better spectral distribution of illumination are discussed

Concept for improved radiometric calibration of radiance sources at the CHB facility

The Calibation Home Base (CHB) is a facility for the calibration of airborne imaging spectrometers such as APEX, ROSIS and in the future ARES, and for field spectrometers. Absolute radiometric calibration in the spectral range of 350–2500 nm is currently based on an integrating sphere whose spectral radiance was calibrated by the German National Metrology Institute PTB. However, a single radiance source cannot meet the requirements of a multitude of sensors, hence CHB operates several sources. In order to enable consistent calibration at CHB, a transfer radiometer based system will be used in the future. Detectors are much more stable than lamps, hence a well-designed system based on accurate detectors can reach much higher absolute accuracy of radiometric calibration than a lamp based set-up. The concept of this system, its hardware components and the expected accuracies are presented

OpAiRS – Optical Airborne Remote Sensing and Calibration Facility

Since 1995 DLR is calibrating and operating airborne imaging spectrometers and is developing software tools for data processing and evaluation for different application fields. In November 2007 this service called “Optical Airborne Remote Sensing and Calibration Facility” (OpAiRS) has been ISO certified (ISO 9001:2000). The Calibration Home Base (CHB) is an optical laboratory for the calibration of airborne hyperspectral sensors and field spectrometers. It was partly funded by ESA and is operational since 2007 within OpAiRS. The automated image processing chain handles system correction, validation and calibration, ortho-rectification, atmospheric correction and quality control for all imagery and metadata OpAiRS also operates different field spectrometers for validation and vicarious calibration of remote sensing data, as well as in-situ measurements for multiple applications. Sensors that are in operation for 2010 and available to the community are DLR’s ROSIS and HyVista’s HyMap sensor

Hydrophilic/Hydrophobic Balance Determines Morphology of Glycolipids with Oligolactose Headgroups

The morphology of synthetic glycolipids with lactose oligomers (Lac N, the number of lactose units, N = 1, 2, 3) was studied in lamellar phase. By a systematic combination of differential scanning calorimetry and small- and wide-angle x-ray scattering experiments, the effects of hydrophilic/hydrophobic balance on their thermotropic phase behaviors were discussed. The dispersion of Lac 1 exhibited a crystalline-fluid phase transition, dominated by the strong van der Waals interaction between dihexadecyl chains. In the case of Lac 2, the hydrophilic/hydrophobic balance between the headgroup and the alkyl chains is shifted to the hydrophilic side, resulting in a gel-fluid phase transition with a decreased transition temperature and phase transition enthalpy. Different from the first two systems, the differential scanning calorimetry trace of Lac 3 showed much less remarkable peaks. The small- and wide-angle x-ray diffraction patterns did not reveal any transition in the chain ordering, suggesting that the correlation between the hexasaccharide headgroups is so strong that the melting of the alkyl chains was not allowed. Such dominant effects of the hydrophilic/hydrophobic balance on the morphology of Lac N lipids can be attributed to the small sterical mismatch between the alkyl chains and the linear, cylindrical oligolactose groups