ORCID Profile
0000-0001-5132-2999
Current Organisations
Universität Hamburg
,
Indian Institute of Technology Madras
,
Max-Planck-Institut für Struktur und Dynamik der Materie
,
Center for Free-Electron Laser Science
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Publications
Femtosecond structural dynamics drives the trans/cis isomerization in photoactive yellow protein
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-05-2016
Abstract: Many biological processes depend on detecting and responding to light. The response is often mediated by a structural change in a protein that begins when absorption of a photon causes isomerization of a chromophore bound to the protein. Pande et al. used x-ray pulses emitted by a free electron laser source to conduct time-resolved serial femtosecond crystallography in the time range of 100 fs to 3 ms. This allowed for the real-time tracking of the trans-cis isomerization of the chromophore in photoactive yellow protein and the associated structural changes in the protein. Science , this issue p. 725
Emergence of Multicolor Photoluminescence in La0.67Sr0.33MnO3 Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 27-11-2012
DOI: 10.1021/JP308606A
Copper Quantum Clusters in Protein Matrix: Potential Sensor of Pb2+ Ion
Publisher: American Chemical Society (ACS)
Date: 17-11-2011
DOI: 10.1021/AC202610E
Abstract: A one-pot synthesis of extremely stable, water-soluble Cu quantum clusters (QCs) capped with a model protein, bovine serum albumin (BSA), is reported. From matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, we assign the clusters to be composed of Cu(5) and Cu(13) cores. The QCs also show luminescence properties having excitation and emission maxima at 325 and 410 nm, respectively, with a quantum yield of 0.15, which are found to be different from that of protein alone in similar experimental conditions. The quenching of luminescence of the protein-capped Cu QCs in the presence of very low hydrogen peroxide concentration (approximately nanomolar, or less than part-per-billion) reflects the efficacy of the QCs as a potential sensing material in biological environments. Moreover, as-prepared Cu QCs can detect highly toxic Pb(2+) ions in water, even at the part-per-million level, without suffering any interference from other metal ions.
Megahertz single-particle imaging at the European XFEL
Publisher: Springer Science and Business Media LLC
Date: 29-05-2020
DOI: 10.1038/S42005-020-0362-Y
Abstract: The emergence of high repetition-rate X-ray free-electron lasers (XFELs) powered by superconducting accelerator technology enables the measurement of significantly more experimental data per day than was previously possible. The European XFEL is expected to provide 27,000 pulses per second, over two orders of magnitude more than any other XFEL. The increased pulse rate is a key enabling factor for single-particle X-ray diffractive imaging, which relies on averaging the weak diffraction signal from single biological particles. Taking full advantage of this new capability requires that all experimental steps, from s le preparation and delivery to the acquisition of diffraction patterns, are compatible with the increased pulse repetition rate. Here, we show that single-particle imaging can be performed using X-ray pulses at megahertz repetition rates. The results obtained pave the way towards exploiting high repetition-rate X-ray free-electron lasers for single-particle imaging at their full repetition rate.
Evaluation of serial crystallographic structure determination within megahertz pulse trains
Publisher: AIP Publishing
Date: 11-2019
DOI: 10.1063/1.5124387
Abstract: The new European X-ray Free-Electron Laser (European XFEL) is the first X-ray free-electron laser capable of delivering intense X-ray pulses with a megahertz interpulse spacing in a wavelength range suitable for atomic resolution structure determination. An outstanding but crucial question is whether the use of a pulse repetition rate nearly four orders of magnitude higher than previously possible results in unwanted structural changes due to either radiation damage or systematic effects on data quality. Here, separate structures from the first and subsequent pulses in the European XFEL pulse train were determined, showing that there is essentially no difference between structures determined from different pulses under currently available operating conditions at the European XFEL.
Protein‐Directed Synthesis of NIR‐Emitting, Tunable HgS Quantum Dots and their Applications in Metal‐Ion Sensing
Publisher: Wiley
Date: 24-07-2012
Abstract: The development of luminescent mercury sulfide quantum dots (HgS QDs) through the bio-mineralization process has remained unexplored. Herein, a simple, two-step route for the synthesis of HgS quantum dots in bovine serum albumin (BSA) is reported. The QDs are characterized by UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, luminescence, Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), circular dichroism (CD), energy dispersive X-ray analysis (EDX), and picosecond-resolved optical spectroscopy. Formation of various sizes of QDs is observed by modifying the conditions suitably. The QDs also show tunable luminescence over the 680-800 nm spectral regions, with a quantum yield of 4-5%. The as-prepared QDs can serve as selective sensor materials for Hg(II) and Cu(II), based on selective luminescence quenching. The quenching mechanism is found to be based on Dexter energy transfer and photoinduced electron transfer for Hg(II) and Cu(II), respectively. The simple synthesis route of protein-capped HgS QDs would provide additional impetus to explore applications for these materials.
Protein-encapsulated gold cluster aggregates: the case of lysozyme
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C2NR33180B
Abstract: We report the evolution and confinement of atomically precise and luminescent gold clusters in a small protein, lysozyme (Lyz) using detailed mass spectrometric (MS) and other spectroscopic investigations. A maximum of 12 Au(0) species could be bound to a single Lyz molecule irrespective of the molar ratio of Lyz : Au(3+) used for cluster growth. The cluster-encapsulated protein also forms aggregates similar to the parent protein. Time dependent studies reveal the emergence of free protein and the redistribution of detached Au atoms, at specific Lyz to Au(3+) molar ratios, as a function of incubation time, proposing inter-protein metal ion transfer. The results are in agreement with the studies of inter-protein metal transfer during cluster growth in similar systems. We believe that this study provides new insights into the growth of clusters in smaller proteins.
Analysis of XFEL serial diffraction data from individual crystalline fibrils
Publisher: International Union of Crystallography (IUCr)
Date: 20-10-2017
DOI: 10.1107/S2052252517014324
Abstract: Serial diffraction data collected at the Linac Coherent Light Source from crystalline amyloid fibrils delivered in a liquid jet show that the fibrils are well oriented in the jet. At low fibril concentrations, diffraction patterns are recorded from single fibrils these patterns are weak and contain only a few reflections. Methods are developed for determining the orientation of patterns in reciprocal space and merging them in three dimensions. This allows the in idual structure litudes to be calculated, thus overcoming the limitations of orientation and cylindrical averaging in conventional fibre diffraction analysis. The advantages of this technique should allow structural studies of fibrous systems in biology that are inaccessible using existing techniques.
Simple convergent-nozzle aerosol injector for single-particle diffractive imaging with X-ray free-electron lasers
Publisher: AIP Publishing
Date: 19-06-2015
DOI: 10.1063/1.4922648
Abstract: A major challenge in high-resolution x-ray free-electron laser-based coherent diffractive imaging is the development of aerosol injectors that can efficiently deliver particles to the peak intensity of the focused X-ray beam. Here, we consider the use of a simple convergent-orifice nozzle for producing tightly focused beams of particles. Through optical imaging we show that 0.5 μm particles can be focused to a full-width at half maximum diameter of 4.2 μm, and we demonstrate the use of such a nozzle for injecting viruses into a micro-focused soft-X-ray FEL beam.
Diffraction data from aerosolized Coliphage PR772 virus particles imaged with the Linac Coherent Light Source
Publisher: Springer Science and Business Media LLC
Date: 19-11-2020
DOI: 10.1038/S41597-020-00745-2
Abstract: Single Particle Imaging (SPI) with intense coherent X-ray pulses from X-ray free-electron lasers (XFELs) has the potential to produce molecular structures without the need for crystallization or freezing. Here we present a dataset of 285,944 diffraction patterns from aerosolized Coliphage PR772 virus particles injected into the femtosecond X-ray pulses of the Linac Coherent Light Source (LCLS). Additional exposures with background information are also deposited. The diffraction data were collected at the Atomic, Molecular and Optical Science Instrument (AMO) of the LCLS in 4 experimental beam times during a period of four years. The photon energy was either 1.2 or 1.7 keV and the pulse energy was between 2 and 4 mJ in a focal spot of about 1.3 μ m x 1.7 μ m full width at half maximum (FWHM). The X-ray laser pulses captured the particles in random orientations. The data offer insight into aerosolised virus particles in the gas phase, contain information relevant to improving experimental parameters, and provide a basis for developing algorithms for image analysis and reconstruction.
Femtosecond X-ray diffraction from an aerosolized beam of protein nanocrystals
Publisher: International Union of Crystallography (IUCr)
Date: 02-2017
DOI: 10.1107/S1600576717018131
Abstract: High-resolution Bragg diffraction from aerosolized single granulovirus nanocrystals using an X-ray free-electron laser is demonstrated. The outer dimensions of the in-vacuum aerosol injector components are identical to conventional liquid-microjet nozzles used in serial diffraction experiments, which allows the injector to be utilized with standard mountings. As compared with liquid-jet injection, the X-ray scattering background is reduced by several orders of magnitude by the use of helium carrier gas rather than liquid. Such reduction is required for diffraction measurements of small macromolecular nanocrystals and single particles. High particle speeds are achieved, making the approach suitable for use at upcoming high-repetition-rate facilities.
Luminescent, bimetallic AuAg alloy quantum clusters in protein templates
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2NR30729D
Abstract: We report the synthesis of luminescent AuAg alloy quantum clusters (QCs) in bovine serum albumin (BSA), for the first time, with experimentally determined atomic composition. Mixing of the as-synthesized protein-protected Au and Ag clusters resulted in the formation of alloy AuAg clusters within the BSA. Mass spectrometric analysis of the product of a 1 : 1 molar ratio reaction mixture of Au(QC)@BSA and Ag(QC)@BSA suggested that the alloy clusters could be Au(38-x)Ag(x)@BSA. Further analyses by standard techniques revealed that the alloy cluster core of ∼1.2 nm diameter is composed of nearly zero valent Au and Ag atoms that exhibit distinctly different steady state and time resolved excited state luminescence profiles compared to the parent clusters. Tuning of the alloy composition was achieved by varying the molar ratio of the parent species in the reaction mixture and compositional changes were observed by mass spectrometry. In another approach, mixing of Au(3+) ions with the as-synthesized Ag(QC)@BSA also resulted in the formation of alloy clusters through galvanic exchange reactions. We believe that alloy clusters with the combined properties of the constituents in versatile protein templates would have potential applications in the future. The work presents interesting aspects of the reactivity of the protein-protected clusters.
Luminescent iron clusters in solution
Publisher: Royal Society of Chemistry (RSC)
Date: 22-06-190728635
DOI: 10.1039/C3NR05784D
Abstract: Metal clusters, composed of a few atoms at the core, exhibit unique properties and have potential applications. Although atomically precise clusters of noble metals have been synthesized, analogous systems of reactive metals, such as iron, have not been realized in solution due to high reactivity. Here we report the synthesis and characterization of novel iron clusters in the hemoglobin matrix that are highly luminescent (quantum yield 10% at 565 nm). The super-paramagnetic iron clusters, after successful ligand exchange from protein and phase transfer from water to chloroform using tri-octylphosphineoxide (TOPO), were detected as [Fe₁₀(TOPO)₃(H₂O)₃](+), [Fe₁₃(TOPO)₂(H₂O)](+) and [Fe₈(TOPO)(H₂O)₂](+) by mass spectrometry. This study lays the groundwork for exploiting unique properties of soluble iron clusters.
Related Organisations
Max-Planck-Institut Für Struktur Und Dynamik Der Materie
Location: Germany
Related Funding Activities
No related grants have been discovered for Paul Lourdu Xavier.