1,031 research outputs found
Multi-slice ptychography with large numerical aperture multilayer Laue lenses
The highly convergent x-ray beam focused by multilayer Laue lenses with large numerical apertures is used as a three-dimensional (3D) probe to image layered structures with an axial separation larger than the depth of focus. Instead of collecting weakly scattered high-spatial-frequency signals, the depth-resolving power is provided purely by the intense central cone diverged from the focused beam. Using the multi-slice ptychography method combined with the on-the-fly scan scheme, two layers of nanoparticles separated by 10 μm are successfully reconstructed with 8.1 nm lateral resolution and with a dwell time as low as 0.05 s per scan point. This approach obtains high-resolution images with extended depth of field, which paves the way for multi-slice ptychography as a high throughput technique for high-resolution 3D imaging of thick samples
Isolation and characterization of antimicrobial, anti-inflammatory and chemopreventive flavones from premna odorata blanco
Premna odorata Blanco (Verbenaceae) is a native tree of the Philippines where its leaves are used traditionally for vaginal irrigation and tuberculosis. It is one of the seven components of a commercialized Philippine herbal preparation called "Pito-Pito". Its medicinal uses, however, have not been scientifically validated. This tree is not commonly cultivated and thrive in the less accessible limestone forests of the Philippines. Solvent partitioning and fractionation of the ethanolic crude extract of the leaves isolated two yellow amorphous powders. The identities of these compounds were determined by LC/MS/MS and NMR spectroscopic analyses, and their spectra were compared with literature data. The isolates were flavone aglycones which were the widespread acacetin and the nonwidespread diosmetin. These flavones were isolated from the P. odorata for the first time ever. They had been reported by earlier studies to exhibit medicinal properties as antimicrobial, anti-inflammatory and chemopreventive. Thus, the current study has provided a scientific evidence of the medicinal properties of the leaves of P. odorata that could become the popular basis for the plant's sustainable use, conservation and cultivation. © 2011 Academic Journals.published_or_final_versio
Performance evaluation of Bragg coherent diffraction imaging
In this study,we present a numerical framework for modeling three-dimensional (3D) diffraction data
in Bragg coherent diffraction imaging (BraggCDI) experiments and evaluating the quality of obtained
3D complex-valued real-space images recovered by reconstruction algorithms under controlled
conditions. The approach is used to systematically explore the performance and the detection limit of
this phase-retrieval-based microscopy tool. The numerical investigation suggests that the superb
performance of Bragg CDI is achieved with an oversampling ratio above 30 and a detection dynamic
range above 6 orders. The observed performance degradation subject to the data binning processes is
also studied. This numerical tool can be used to optimize experimental parameters and has the
potential to significantly improve the throughput of Bragg CDI method
Nucleophilic substitution by amide nitrogen in the aromatic rings of [zn − H]˙+ ions; the structures of the [b2 − H − 17]˙+ and [c1 − 17]+ ions
Peptide radical cations that contain an aromatic amino acid residue cleave to give [zn − H]˙+ ions with [b2 − H − 17]˙+ and [c1 − 17]+ ions, the dominant products in the dissociation of [zn − H]˙+, also present in lower abundance in the CID spectra. Isotopic labeling in the aromatic ring of [Yπ˙GG]+ establishes that in the formation of [b2 − H − 17]˙+ ions a hydrogen from the δ-position of the Y residue is lost, indicating that nucleophilic substitution on the aromatic ring has occurred. A preliminary DFT investigation of nine plausible structures for the [c1 − 17]+ ion derived from [Yπ˙GG]+ shows that two structures resulting from attack on the aromatic ring by oxygen and nitrogen atoms from the peptide backbone have significantly better energies than other isomers. A detailed study of [Yπ˙GG]+ using two density functionals, B3LYP and M06-2X, with a 6-31++G(d,p) basis set gives a higher barrier for attack on the aromatic ring of the [zn − H]˙+ ion by nitrogen than by the carbonyl oxygen. However, subsequent rearrangements involving proton transfers are much higher in energy for the oxygen-substituted isomer leading to the conclusion that the [c1 − 17]+ ions are the products of nucleophilic attack by nitrogen, protonated 2,7-dihydroxyquinoline ions. The [b2 − H − 17]˙+ ions are formed by loss of glycine from the same intermediates involved in the formation of the [c1 − 17]+ ions.postprin
Formation and Dissociation of Phosphorylated Peptide Radical Cations
published_or_final_versio
Artifact mitigation of ptychography integrated with on-the-fly scanning probe microscopy
We report our experiences with conducting ptychography simultaneously with the X-ray fluorescence
measurement using the on-the-fly mode for efficient multi-modality imaging. We demonstrate
that the periodic artifact inherent to the raster scan pattern can be mitigated using a
sufficiently fine scan step size to provide an overlap ratio of >70%. This allows us to obtain transmitted
phase contrast images with enhanced spatial resolution from ptychography while maintaining
the fluorescence imaging with continuous-motion scans on pixelated grids. This capability
will greatly improve the competence and throughput of scanning probe X-ray microscopy
Resolution-enhanced X-ray fluorescence microscopy via deep residual networks
Multimodal hard X-ray scanning probe microscopy has been extensively used to study functional materials providing multiple contrast mechanisms. For instance, combining ptychography with X-ray fluorescence (XRF) microscopy reveals structural and chemical properties simultaneously. While ptychography can achieve diffraction-limited spatial resolution, the resolution of XRF is limited by the X-ray probe size. Here, we develop a machine learning (ML) model to overcome this problem by decoupling the impact of the X-ray probe from the XRF signal. The enhanced spatial resolution was observed for both simulated and experimental XRF data, showing superior performance over the state-of-the-art scanning XRF method with different nano-sized X-ray probes. Enhanced spatial resolutions were also observed for the accompanying XRF tomography reconstructions. Using this probe profile deconvolution with the proposed ML solution to enhance the spatial resolution of XRF microscopy will be broadly applicable across both functional materials and biological imaging with XRF and other related application areas
Extending the depth of field for ptychography using complex-valued wavelets
Ptychography is a scanning variation of the coherent diffractive imaging method for providing high-resolution
quantitative images from specimen with extended dimensions. Its capability of achieving diffraction-limited spatial
resolution can be compromised by the sample thickness,
which is generally required to be thinner than the depth
of field of the imaging system. In this Letter, we present
a method to extend the depth of field for ptychography
by numerically generating the focus stack from reconstructions with propagated illumination wavefronts and combining the in-focus features to a single sharp image using an
algorithm based on the complex-valued discrete wavelet
transform. This approach does not require repeated measurements by translating the sample along the optical axis
as in the conventional focus stacking method, and offers a
computation-efficient alternative to obtain high-resolution
images with extended depth of fields, complementary to the
multi-slice ptychography
Fully Automatable Two-dimensional HILIC–RP Liquid Chromatography with Online Tandem Mass Spectrometry for Shotgun Proteomics
Poster PresentationConference theme: Proteomics: Better for lifeMultidimensional liquid chromatography (MDLC) which multiples the resolution power of individual dimension with high orthogonality
is a very efficient front-end separation method for analyzing the digests of complex biological samples. Among the existing two
dimensional liquid chromatography (2DLC) systems, the combination of hydrophilic interaction liquid chromatography (HILIC)
followed by low-pH reversed-phase (RP)LC (HILIC-RP) has very high orthogonality and is a very promising 2DLC method. Herein,
a fully automatable two-dimensional (2D) liquid chromatography system was developed for shotgun proteomics analyses, which
coupling the hydrophilic interaction liquid chromatography (HILIC) TSKgel Amide 80 (a non-ionic type) with the low-pH reversedphase
(RP) chromatography. The performance of the 2D HILIC-RP LC platform was investigated at both pH 6.8 (neutral pH) and
pH 2.7 (acidic pH) of the first dimension HILIC column by duplicate analyses of a Rat pheochromocytoma lysates.Online coupling
of the neutral-pH HILIC and RP systems outperformedthe acidic HILIC–RP combination,resulting in 18.4% (1914 versus 1617 nonredundant
proteins) and 41.6% (12,989 versus 9172unique peptides) increases in the number of identified proteins and peptides.
To further test the established 2D HILIC-RP platform, we identified 2648 non-redundant proteins from triplicate analyses of a
Saccharomyces cerevisiae lysate, with the detected protein abundances spanning from approximately41 to 106 copies per cell,
which contained up to 2164 different validated protein species with a dynamic range of concentrations up to approximately 104.
Herein, this studyestablished a fully automated 2D liquid chromatography platform to enable onlinecoupling of different HILIC and
RP chromatography systems, thereby expanding the choice and application of multidimensional liquid chromatography for shotgun
proteomics.published_or_final_versio
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