A5087503618- Force Microscopy Techniques and Applications
- Electron Spin Resonance Studies
- Mechanical and Optical Resonators
- Lipid Membrane Structure and Behavior
- Advanced NMR Techniques and Applications
- Photoreceptor and optogenetics research
- Integrated Circuits and Semiconductor Failure Analysis
- Magnetism in coordination complexes
- Photochemistry and Electron Transfer Studies
- Spectroscopy and Quantum Chemical Studies
- Advanced Electron Microscopy Techniques and Applications
- Bacteriophages and microbial interactions
- Lanthanide and Transition Metal Complexes
- Solid-state spectroscopy and crystallography
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Materials Characterization Techniques
- Nonlinear Dynamics and Pattern Formation
- Terahertz technology and applications
- Physics of Superconductivity and Magnetism
- thermodynamics and calorimetric analyses
- Congenital Anomalies and Fetal Surgery
- Nonlinear Photonic Systems
- Biochemical and Structural Characterization
- Glycosylation and Glycoproteins Research
- Algal biology and biofuel production
National Institute of Standards and Technology
2015-2021
University of Colorado Boulder
2015-2021
University of California, Santa Barbara
2010-2020
Joint Institute for Laboratory Astrophysics
2020
Colgate University
2014
Santa Barbara City College
2014
Virginia Tech
2000
Fermi National Accelerator Laboratory
2000
Protein folding occurs as a set of transitions between structural states within an energy landscape. An oversimplified view the process emerges when transiently populated are undetected because limited instrumental resolution. Using force spectroscopy optimized for 1-microsecond resolution, we reexamined unfolding individual bacteriorhodopsin molecules in native lipid bilayers. The experimental data reveal pathway unprecedented detail. Numerous newly detected intermediates-many separated by...
We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed gain (approximately 3000) and radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, intensity fluctuations, are all consistent with models for SASE FELs.
ABSTRACT The structure of the viscous extracellular polysaccharide (glycan) desiccation-tolerant Nostoc commune DRH-1 was determined through chromatographic and spectroscopic methods. is novel in that it possesses a 1-4-linked xylogalactoglucan backbone with d -ribofuranose 3- O -[( R )-1-carboxyethyl]- -glucuronic acid (nosturonic acid) pendant groups. presence -ribose nosturonic as peripheral groups unusual, their potential roles modulating rheological properties glycan are discussed....
Atomic force microscopy (AFM)-based single-molecule spectroscopy (SMFS) is a powerful yet accessible means to characterize mechanical properties of biomolecules. Historically, accessibility relies upon the nonspecific adhesion biomolecules surface and cantilever and, for proteins, integration target protein into polyprotein. However, this assay results in low yield high-quality data, defined as complete unfolding Additionally, hinders studies α-helical which unfold at forces extensions....
Atomic force microscopy (AFM)-based single-molecule spectroscopy (SMFS) is widely used to mechanically measure the folding and unfolding of proteins. However, temporal resolution a standard commercial cantilever 50-1000 μs, masking rapid transitions short-lived intermediates. Recently, SMFS with 0.7-μs was achieved using an ultrashort (L = 9 μm) on custom-built, high-speed AFM. By micromachining such cantilevers focused ion beam, we optimized them for rather than tapping-mode imaging. To...
Optimum integral EPR saturation, determined by electron <italic>T</italic><sub>1e</sub> and spin flip-flop rate, maximizes solid-state DNP performance using nitroxide radicals.
We present our experimental setup for both dynamic nuclear polarization (DNP) and electron paramagnetic resonance (EPR) detection at 7 T using a quasi-optical bridge propagation of the 200 GHz beam initial results obtained 4 K. Our allows microwave to be changed from linear circular. Only handedness circular in direction Larmor precession is absorbed by spins, so gain effective power two expected vs. polarization. show an increase DNP signal enhancement 28% when circularly linearly polarized...
Interspin distances between 0.8 nm and 2.0 can be measured through the dipolar broadening of continuous wave (cw) EPR spectrum nitroxide spin labels at X-band (9.4 GHz, 0.35 T). We introduce Gd3+ as a promising alternative label for distance measurements by cw above 7 Tesla, where |−1/2〉 to |1/2〉 transition narrows below 1 mT becomes extremely sensitive broadening. To estimate limits with Gd3+, we have spectra frozen solutions GdCl3 8.6 T (240 GHz) 10 K concentrations ranging from 50 mM 0.1...
Significance Atomic force microscopy (AFM) is widely applied to unfold proteins. Using advanced cantilevers in a commercial AFM improve stability and precision, we unfolded then refolded an individual fast-folding, mechanically labile protein—a technically challenging sample—thousands of times. To address concerns that the measured dynamics such proteins are dominated by assay, modulated protein’s folding rate using pH. Kinetic analysis demonstrated changes free-energy landscape parameters...
In order to facilitate versatile applications with high field dynamic nuclear polarization (DNP), it is important be able optimize the DNP performance, i.e. reach hyperpolarization within a short signal build up time. Given that solid-state process strongly temperature-dependent, benchmark temperature dependence of various and electron paramagnetic resonance (EPR) parameters can then used test develop theories models for mechanisms. However, EPR experiments at fields cryogenic temperatures...
The forces that stabilize membrane proteins remain elusive to precise quantification. Particularly important, but poorly resolved, are the present during initial unfolding of a protein, where most native set interactions is present. A high-precision, atomic force microscopy assay was developed study bacteriorhodopsin. rapid near-equilibrium folding between first three states discovered, two transitions corresponded five and amino acids, respectively, when using cantilever optimized for 2 μs...
A simple, compact, high-performance absorbing load (absorber) for narrow-band THz spectroscopy is described. Current commercially available absorbers offering more than 20 dB return loss are bulky, made of proprietary materials, and intrinsically broadband. This 240 GHz absorber consists a precisely machined thin layer PMMA (plexiglas) placed over small volume water. By diluting the water with glycerol, effective refractive index back medium may be adjusted finely to maximize loss. The...
Electron paramagnetic resonance (EPR) powered by a free electron laser (FEL) has been shown to dramatically expand the capabilities of EPR at frequencies above ~100 GHz, where other high-power sources are unavailable. High-power pulses necessary achieve fast (<10 ns) spin rotations in order alleviate limited excitation bandwidth and time resolution that typically hamper pulsed these high frequencies. While frequencies, an FEL is only source provides ~1 kW power can be tuned continuously up 1...
Evaluation of abnormal adult chest computed tomography (CT) scans.Retrospective series 3 cases.Two University-based hospitals.Three patients (age range 56 to 61) underwent CT scans. Two were trauma and one complained pain with a negative cardiac workup. One scan revealed lung mass that was highly suspicious for malignancy the other two scans diaphragmatic hernia. elective surgery third emergent surgery.The patient 1 malignancy; however, pathology only inflammation consistent an intralobular...
We present experimental evidence for a new behavior which involves discrete breathers and vortices in Josephson Ladder. Breathers can be visualized as the creation subsequent annihilation of vortex/anti-vortex pairs. An externally applied magnetic field breaks symmetry causes breather to split apart. The motion vortex or anti-vortex creates multi-site breathers, are always one side other original depending on sign field. This asymmetry is experimentally observed.
Free electron laser-powered pulsed paramagnetic resonance experiments performed at 240 GHz/8.56 T on the crystalline organic radical 1,3-bisdiphenylene-2-phenylallyl reveal a tip-angle dependent resonant frequency. Frequency shifts as large 11 MHz (45 ppm) are observed during single Rabi oscillation. We attribute frequency to "dressing" of nutation by spin-spin interactions. A nonlinear semiclassical model which includes temperature- and sample-geometry-dependent demagnetizing field...
Abstract The forces that stabilize membrane proteins remain elusive to precise quantification. Particularly important, but poorly resolved, are the present during initial unfolding of a protein, where most native set interactions is present. A high‐precision, atomic force microscopy assay was developed study bacteriorhodopsin. rapid near‐equilibrium folding between first three states discovered, two transitions corresponded five and amino acids, respectively, when using cantilever optimized...
We describe a focused ion beam system and spectroscopic technique that utilize photons emitted from electronically excited sputtered neutrals for surface element identification end-point detection. When target is bombarded by beam, some of the atoms (as much as 0.2%) leave in states then quickly decay (10−6–10−8 s) emitting characteristic energies. A sputter-induced optical emission spectrometer elemental imaging were constructed using conjunction with wavelength-selectable photon detector....