Amyloid fibrils have been implicated in the pathogenesis of several neurodegenerative diseases, the most prevalent example being Alzheimer's disease (AD). Despite the prevalence of AD, relatively little is known about the structure of the associated amyloid fibrils. This has motivated our studies of fibril structures, extended here to the familial Arctic mutant of A beta(1-42), E22G-A beta(1-42). We found E22G-A beta(M0,1-42) is toxic to Escherichia coli, thus we expressed E22G-A beta(1-42) fused to the self-cleavable tag N-Pro in the form of its EDDIE mutant. Since the high surface activity of E22G-A beta(1-42) makes it difficult to obtain more than sparse quantities of fibrils, we employed H-1 detected magic angle spinning (MAS) nuclear magnetic resonance (NMR) experiments to characterize the protein. The H-1 detected C-13-C-13 methods were first validated by application to fully protonated amyloidogenic nanocrystals of GNNQQNY, and then applied to fibrils of the Arctic mutant of A beta, E22G-A beta(1-42). The MAS NMR spectra indicate that the biosynthetic samples of E22G-A beta(1-42) fibrils comprise a single conformation with C-13 chemical shifts extracted from hCH, hNH, and hCCH spectra that are very similar to those of wild type A beta(1-42) fibrils. These results suggest that E22G-A beta(1-42) fibrils have a structure similar to that of wild type A beta(1-42).

Laser processing of diamond has become an important technique for fabricating next generation microelectronic and quantum devices. However, the realization of low taper, high aspect ratio structures in diamond remains a challenge. We demonstrate the effects of pulse energy, pulse number and irradiation profile on the achievable aspect ratio with 532 nm nanosecond laser machining. Strong and gentle ablation regimes were observed using percussion hole drilling of type Ib HPHT diamond. Under percussion hole drilling a maximum aspect ratio of 22:1 was achieved with 10,000 pulses. To reach aspect ratios on average 40:1 and up to 66:1, rotary assisted drilling was employed using > 2 M pulse accumulations. We additionally demonstrate methods of obtaining 0.1° taper angles via ramped pulse energy machining in 10:1 aspect ratio tubes. Finally, effects of laser induced damage are studied using confocal Raman spectroscopy with observation of up to 36% increase in tensile strain following strong laser irradiation. However, we report that upon application of 600 °C heat treatment, induced strain is reduced by up to ~ 50% with considerable homogenization of observed strain.

The resolution of magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra remains bounded by the spinning frequency, which is limited by the material strength of MAS rotors. Since dia-mond is capable of withstanding 1.5-2.5x greater MAS frequencies, compared to state-of-the art zirconia, we fabricated rotors from single crystal diamond. When combined with bearings optimized for spinning with helium gas, diamond rotors could achieve the highest MAS frequencies to date. Furthermore, the excellent microwave transmission properties and thermal conductivity of diamond could improve sensi-tivity enhancements in dynamic nuclear polarization (DNP) experiments. The fabrication protocol we report involves novel laser micromachining and produced rotors that presently spin at xr=2p= 111.000 & PLUSMN; 0.004 kHz, with stable spinning up to 124 kHz, using N2 gas as the driving fluid. We present the first proton-detected 13C/15N MAS spectra recorded using diamond rotors, a critical step towards studying currently inaccessible ex-vivo protein samples with MAS NMR. Previously, the high aspect ratio of MAS rotors (-10:1) precluded fabrication of MAS rotors from diamond.& COPY; 2023 Elsevier Inc. All rights reserved.

This chapter provides an overview of 3D printing technology related to the development of novel instrumentation for analytical techniques in spectroscopy. These techniques include spectrophotometry, infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance spectroscopy. In many cases, the required tolerances, material properties, and design complexity push the capabilities of current 3D-printing technology to the limit. For each analytical technique, we outline recent instrumentation developments using different 3D-printing methods and the impact this technology has had on fields ranging from materials science to structural biology. We further detail the technical challenges and outlook for the fabrication of the next generation of state-of-the-art scientific devices. Finally, we discuss the implications of 3D printing as a digital fabrication method that provides improved access to and rapid iteration of scientific devices and instrumentation.

The Overhauser effect (OE), commonly observed in NMR spectra of liquids and conducting solids, was recently discovered in insulating solids doped with the radical 1,3-bisdiphenylene-2-phenylallyl (BDPA). However, the mechanism of polarization transfer in OE-DNP in insulators is yet to be established, but hyperfine coupling of the radical to protons in BDPA has been proposed. In this paper we present a study that addresses the role of hyperfine couplings via the EPR and DNP measurements on some selectively deuterated BDPA radicals synthesized for this purpose. Newly developed synthetic routes enable selective deuteration at orthogonal positions or perdeuteration of the fluorene moieties with 2H incorporation of >93%. The fluorene moieties were subsequently used to synthesize two octadeuterated BDPA radicals, 1,3-[α,γ-d8]-BDPA and 1,3-[β,δ-d8]-BDPA, and a BDPA radical with perdeuterated fluorene moieties, 1,3-[α,β,γ,δ-d16]-BDPA. In contrast to the strong positive OE enhancement observed in degassed samples of fully protonated h21-BDPA (ε ∼ +70), perdeuteration of the fluorenes results in a negative enhancement (ε ∼ -13), while selective deuteration of α- and γ-positions (aiso ∼ 5.4 MHz) in BDPA results in a weak negative OE enhancement (ε ∼ -1). Furthermore, deuteration of β- and δ-positions (aiso ∼ 1.2 MHz) results in a positive OE enhancement (ε ∼ +36), albeit with a reduced magnitude relative to that observed in fully protonated BDPA. Our results clearly show the role of the hyperfine coupled α and γ 1H spins in the BDPA radical in determining the dominance of the zero and double-quantum cross-relaxation pathways and the polarization-transfer mechanism to the bulk matrix.

3D printing has evolved into an invaluable tool for rapid and cost-effective production of intricate parts. In this paper we describe 3D printing and other rapid prototyping methods to fabricate 3.2 mm stators and drive caps for use in magic angle spinning (MAS) NMR experiments. These components can be fabricated with the assistance of computer-aided design (CAD) software and at a fraction of the cost of commercial parts. Additionally, we show that the performance of these 3D printed stators and drive caps is comparable to commercially available systems and that they have significant advantages over their machined counterparts. (C) 2021 Elsevier Inc. All rights reserved.

Dynamic nuclear polarization (DNP) with cryogenic magic angle spinning (MAS) provides significant improvements in NMR sensitivity, yet presents unique technical challenges. Here we describe a custom cryostat and suite of NMR probes capable of manipulating nuclear spins with multi-resonant radiofrequency circuits, cryogenic spinning below 6 K, sample exchange, and microwave coupling for DNP. The corrugated waveguide and six transfer lines needed for DNP and cryogenic spinning functionality are coupled to the probe from the top of the magnet. Transfer lines are vacuum-jacketed and provide bearing and drive gas, variable temperature fluid, two exhaust pathways, and a sample ejection port. The cryostat thermally isolates the magnet bore, thereby protecting the magnet and increasing cryogen efficiency. This novel design supports cryogenic MAS-DNP performance over an array of probes without altering DNP functionality. We present three MAS probes (two supporting 3.2 mm rotors and one supporting 9.5 mm rotors) interfacing with the single cryostat. Mechanical details, transmission line radio frequency design, and performance of the cryostat and three probes are described. (C) 2018 Published by Elsevier Inc.

We describe a frequency-agile gyrotron which can generate frequency-chirped microwave pulses. An arbitrary waveform generator (AWG) within the NMR spectrometer controls the microwave frequency, enabling synchronized pulsed control of both electron and nuclear spins. We demonstrate that the acceleration of emitted electrons, and thus the microwave frequency, can be quickly changed by varying the anode voltage. This strategy results in much faster frequency response than can be achieved by changing the potential of the electron emitter, and does not require a custom triode electron gun. The gyrotron frequency can be swept with a rate of 20 MHz/mu s over a 670 MHz bandwidth in a static magnetic field. We have already implemented time-domain electron decoupling with dynamic nuclear polarization (DNP) magic angle spinning (MAS) with this device. In this contribution, we show frequency-swept DNP enhancement profiles recorded without changing the NMR magnet or probe. The profile of endofullerenes exhibits a DNP profile with a <10 MHz linewidth, indicating that the device also has sufficient frequency stability, and therefore phase stability, to implement pulsed DNP mechanisms such as the frequency-swept solid effect. We describe schematics of the mechanical and vacuum construction of the device which includes a novel flanged sapphire window assembly. Finally, we discuss how commercially available continuous-wave gyrotrons can potentially be converted into similar frequency-agile high-power microwave sources. (C) 2018 Published by Elsevier Inc.