Design, Fabrication and Analysis of a Hybrid-Order Monolithic Imaging Diffractive Lens on a Germanium Substrate.

Diffractive optical elements are gradually replacing some conventional optical elements and becoming a key component of optical systems due to their unique phase modulation function. However, the imaging performance will be reduced due to the fact that this single-sided microstructured lens still produces chromatic aberration. Therefore, the key issue for the application of diffractive optical elements in optical systems is the reduction of chromatic aberration, and diffractive lenses with double-sided microstructures are proposed as a solution. This research describes the design and analysis of a 70-mm-diameter, 296-mm-focal-length double-sided microstructured hybrid-order monolithic imaging diffractive lens operating in the mid-wave infrared region (3.7-4.7 µm). The design minimizes chromatic aberration by up to 30 times compared to a standard harmonic diffractive lens and improves the image performance of a single-lens optical system operating in the infrared range. Experiments indicate that this design is capable of achieving single-lens imaging with high sensitivity for optical systems with a measured NETD ≤ 50 mK. The analysis of the experiments yielded suggestions for future research.

Electron-Activated Tandem Mass Spectrometry Analysis of Glycosaminoglycans.

Glycosaminoglycans (GAGs) are linear polysaccharides found in a variety of organisms. GAGs contribute to biochemical pathway regulation, cell signaling, and disease progression. GAG sequence information is imperative for determining structure-function relationships. Recent advances in electron-activation techniques paired with high-resolution mass spectrometry allow for full sequencing of GAG structures. Electron detachment dissociation (EDD) and negative electron transfer dissociation (NETD) are two electron-activation methods that have been utilized for GAG characterization. Both methods produce an abundance of informative glycosidic and cross-ring fragment ions without producing a high degree of sulfate decomposition. Here, we provide detailed protocols for using EDD and NETD to sequence GAG chains. In addition to protocols directly involving performing these MS/MS methods, protocols include sample preparation, method development, internal calibration, and data analysis. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Preparation of glycosaminoglycan samples Basic Protocol 2: FTICR method development Basic Protocol 3: Internal calibration with NaTFA Basic Protocol 4: Electron Detachment Dissociation (EDD) of GAG samples Basic Protocol 5: Negative electron transfer dissociation (NETD) of GAG samples Basic Protocol 6: Analysis of MS/MS data.

Negative Electron Transfer Dissociation Sequencing of Increasingly Sulfated Glycosaminoglycan Oligosaccharides on an Orbitrap Mass Spectrometer.

The structural characterization of sulfated glycosaminoglycan (GAG) carbohydrates remains an important target for analytical chemists attributable to challenges introduced by the natural complexity of these mixtures and the defined need for molecular-level details to elucidate biological structure-function relationships. Tandem mass spectrometry has proven to be the most powerful technique for this purpose. Previously, electron detachment dissociation (EDD), in comparison to other methods of ion activation, has been shown to provide the largest number of useful cleavages for de novo sequencing of GAG oligosaccharides, but such experiments are restricted to Fourier transform ion cyclotron resonance mass spectrometers (FTICR-MS). Negative electron transfer dissociation (NETD) provides similar fragmentation results, and can be achieved on any mass spectrometry platform that is designed to accommodate ion-ion reactions. Here, we examine for the first time the effectiveness of NETD-Orbitrap mass spectrometry for the structural analysis of GAG oligosaccharides. Compounds ranging in size from tetrasaccharides to decasaccharides were dissociated by NETD, producing both glycosidic and cross-ring cleavages that enabled the location of sulfate modifications. The highly-sulfated, heparin-like synthetic GAG, ArixtraTM, was also successfully sequenced by NETD. In comparison to other efforts to sequence GAG chains without fully ionized sulfate constituents, the occurrence of sulfate loss peaks is minimized by judicious precursor ion selection. The results compare quite favorably to prior results with electron detachment dissociation (EDD). Significantly, the duty cycle of the NETD experiment is sufficiently short to make it an effective tool for on-line separations, presenting a straightforward path for selective, high-throughput analysis of GAG mixtures. Graphical Abstract ᅟ.