Heterogeneous Ice Growth in Micron-Sized Water Droplets Due to Spontaneous Freezing

Understanding how ice nucleates and grows into larger crystals is of crucial importance for many research fields. The purpose of this study was to shed light on the phase and structure of ice once a nucleus is formed inside a metastable water droplet. Wide-angle X-ray scattering (WAXS) was performed on micron-sized droplets evaporatively cooled to temperatures where homogeneous nucleation occurs. We found that for our weak hits ice grows more cubic compared to the strong hits that are completely hexagonal. Due to efficient heat removal caused by evaporation, we propose that the cubicity of ice at the vicinity of the droplet’s surface is higher than for ice formed within the bulk of the droplet. Moreover, the Bragg peaks were classified based on their geometrical shapes and positions in reciprocal space, which showed that ice grows heterogeneously with a significant population of peaks indicative of truncation rods and crystal defects. Frequent occurrences of the (100) reflection with extended in-planar structure suggested that large planar ice crystals form at the droplet surface, then fracture into smaller domains to accommodate to the curvature of the droplets. Planar faulting due to misaligned domains would explain the increased cubicity close to the droplet surface.

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The damping of terahertz acoustic modes in aqueous nanoparticle suspensions

Scientific Reports ◽

10.1038/s41598-021-99503-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Alessio De Francesco ◽

Luisa Scaccia ◽

Ferdinando Formisano ◽

Eleonora Guarini ◽

Ubaldo Bafile ◽

...

Keyword(s):

Bayesian Analysis ◽

Relative Concentration ◽

Acoustic Mode ◽

Acoustic Damping ◽

Longitudinal Acoustic ◽

X Ray ◽

Acoustic Modes ◽

X Ray Scattering ◽

Nanoparticle Suspensions ◽

Shed Light

AbstractIn this work, we investigate the possibility of controlling the acoustic damping in a liquid when nanoparticles are suspended in it. To shed light on this topic, we performed Inelastic X-Ray Scattering (IXS) measurements of the terahertz collective dynamics of aqueous suspensions of nanospheres of various materials, size, and relative concentration, either charged or neutral. A Bayesian analysis of measured spectra indicates that the damping of the two acoustic modes of water increases upon nanoparticle immersion. This effect seems particularly pronounced for the longitudinal acoustic mode, which, whenever visible at all, rapidly damps off when increasing the exchanged wavevector. Results also indicate that the observed effect strongly depends on the material the immersed nanoparticles are made of.

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ATP/ADP modulates gp16–pRNA conformational change in the Phi29 DNA packaging motor

Nucleic Acids Research ◽

10.1093/nar/gkz692 ◽

2019 ◽

Vol 47 (18) ◽

pp. 9818-9828 ◽

Cited By ~ 2

Author(s):

Rujie Cai ◽

Ian R Price ◽

Fang Ding ◽

Feifei Wu ◽

Ting Chen ◽

...

Keyword(s):

Small Angle ◽

3D Models ◽

Dna Packaging ◽

Conformation Change ◽

Packaging Process ◽

X Ray ◽

X Ray Scattering ◽

Chemical Probing ◽

Dna Packaging Motor ◽

Shed Light

Abstract Packaging of phage phi29 genome requires the ATPase gp16 and prohead RNA (pRNA). The highly conserved pRNA forms the interface between the connector complex and gp16. Understanding how pRNA interacts with gp16 under packaging conditions can shed light on the molecular mechanism of the packaging motor. Here, we present 3D models of the pRNA–gp16 complex and its conformation change in response to ATP or ADP binding. Using a combination of crystallography, small angle X-ray scattering and chemical probing, we find that the pRNA and gp16 forms a ‘Z’-shaped complex, with gp16 specifically binds to pRNA domain II. The whole complex closes in the presence of ATP, and pRNA domain II rotates open as ATP hydrolyzes, before resetting after ADP is released. Our results suggest that pRNA domain II actively participates in the packaging process.

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Solvent-mediated conductance increase of dodecanethiol-stabilized gold nanoparticle monolayers

Beilstein Journal of Nanotechnology ◽

10.3762/bjnano.7.196 ◽

2016 ◽

Vol 7 ◽

pp. 2057-2064 ◽

Cited By ~ 2

Author(s):

Patrick A Reissner ◽

Jean-Nicolas Tisserant ◽

Antoni Sánchez-Ferrer ◽

Raffaele Mezzenga ◽

Andreas Stemmer

Keyword(s):

Gold Nanoparticle ◽

Organic Molecules ◽

Pure Ethanol ◽

X Ray ◽

X Ray Scattering ◽

Average Factor ◽

Respective Contribution ◽

Conductance Increase ◽

Shed Light

Gold nanoparticle monolayers provide convenient templates to study charge transport in organic molecules beyond single junction techniques. Conductance is reported to increase by several orders of magnitude following immersion of alkanethiol-stabilized gold nanoparticle monolayers in a solution containing conjugated thiol-functionalized molecules. Typically, this observation is attributed to molecular exchange. Less attention has been paid to the role of the solvent alone. Here, we report on an increase in conductance of dodecanethiol-stabilized gold nanoparticle monolayers on Si/SiO2 by an average factor of 36 and 22 after immersion in pure ethanol (EtOH) and tetrahydrofuran (THF), respectively. Analysis by scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS) reveals a solvent-induced decrease in lattice constant of close-packed monolayers. We compare the conductance of the monolayer after molecular exchange with two different oligophenylenes to shed light on the respective contribution of the solvent-induced structural change and the molecular exchange itself on the conductance increase.

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CREDO: a new general-purpose laboratory instrument for small-angle X-ray scattering

Journal of Applied Crystallography ◽

10.1107/s1600576714019918 ◽

2014 ◽

Vol 47 (5) ◽

pp. 1749-1754 ◽

Cited By ~ 22

Author(s):

András Wacha ◽

Zoltán Varga ◽

Attila Bóta

Keyword(s):

Small Angle ◽

Academic Research ◽

General Purpose ◽

X Ray ◽

Research Fields ◽

X Ray Scattering ◽

Recent Developments ◽

Instrument Control ◽

High Degree ◽

Ray Scattering

The details of a newly constructed small-angle X-ray scattering instrument are presented. The geometry of the instrument is highly customizable, enabling it to address vastly different experimental situations from academic research to industrial problems. The high degree of motorization and automation compared to conventional laboratory-scale SAXS instruments facilitates the alignment and daily use. Data reduction routines are incorporated in the instrument control software, yielding fully corrected and calibrated results promptly after the end of measurements. Optimization of the fluxversus resolution balance can be done routinely for each measurement task. A wide, continuous range ofq= 4πsinθ/λ can be reached, from below 0.02 nm−1up to 30 nm−1, corresponding to periodic distances ofca 350 nm down to 0.2 nm. A few representative results obtained from samples of different research fields demonstrate the versatility of the instrument. Scattering curves are routinely calibrated into absolute units using a glassy carbon secondary standard. More information and recent developments can be found on the web page of the instrument at http://credo.ttk.mta.hu.

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Hierarchical Assembly Pathways of Spermine Induced Tubulin Conical-Spiral Architectures

10.26434/chemrxiv.11353166.v1 ◽

2019 ◽

Author(s):

Raviv Dharan ◽

Asaf Shemesh ◽

Abigail Millgram ◽

Yael Levi-Kalisman ◽

Israel Ringel ◽

...

Keyword(s):

Self Assembly ◽

Hexagonal Lattice ◽

Building Blocks ◽

Time Resolved ◽

X Ray ◽

Hierarchical Assembly ◽

Research Fields ◽

X Ray Scattering ◽

Assembly Pathways ◽

Ray Scattering

Tubulin dimers are flexible entities serving as building blocks for construction of cellular polymers essential for the cytoskeleton. The conformational state of the dimer dictates the exact formation of assembly and can be regulated by cellular factors including spermine. Using solution X-ray scattering and cryo-TEM measurements we studied the behavior of tubulin assembly in the presence of millimolar spermine concentrations. The results discovered novel structural architectures of tubulin polymers and revealing fascinating hierarchical self-associations based on unique tubulin conical-spiral (TCS) subunits. We followed the assembly pathways of tubulin dimers with different spermine concentrations, from milliseconds to days, and discovered multiple phase transitions with increasing spermine concentration. At 1 mM spermine, tubulin assembled into tubulin helical-pitch (THP) structures, resembling tubulin-rings. Above 1.5 mM spermine, tubulin assembled into TCS architectures. TCS is a unique tubulin assembly, serving as a new building block subunit. TCS assembled into different architectures . The predominant structure was TCS-tube (TCST) that further assembled in a remarkable antiparallel orientation which formed bundles with 2D-cubic and unique quasi-2D hexagonal lattices. Each TCST in the quasi-2D hexagonal lattice was surrounded by four antiparallel TCSTs and two parallel TCSTs. All the above assemblies have never been observed before. At higher spermine concentrations, tubulin assembled into twisted inverted tubulin tubules (ITTs). Here we also show for the first time, the hierarchical assembly pathways from tubulin dimer to each of the above structures, using time-resolved experiments with millisecond temporal resolution. We discovered that the structures that formed at low spermine concentrations were transient precursors of the structures formed at higher spermine concentrations. The results are based on high quality cryo-TEM images, cutting edge synchrotron solution X-ray scattering measurements and state-of-the-art data analysis, using our home developed groundbreaking analysis software, D+. The findings can be relevant to a broad research fields including studies which explore different arrangements of the cytoskeletal network, or studies exploring the attraction forces between proteins that dictate their mode of assembly and molecular designed self-assembly of natural and/or synthetic analogous.

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Flow-Induced Crystallization in Polyethylene: Effect of Flow Time on Development of Shish-Kebab

Polymers ◽

10.3390/polym12112571 ◽

2020 ◽

Vol 12 (11) ◽

pp. 2571

Author(s):

Ruijun Zhao ◽

Zhaozhe Chu ◽

Zhe Ma

Keyword(s):

Flow Time ◽

Isothermal Process ◽

X Ray ◽

Flow Duration ◽

X Ray Scattering ◽

The Stability ◽

Induced Crystallization ◽

Shed Light ◽

Identical Strain ◽

Flow Induced Crystallization

The flow-induced formation and relaxation of the representative oriented shish-kebab structure were studied with synchrotron small-angle X-ray scattering (SAXS) method. The flow duration was varied from 2 to 6 s at an identical strain rate to reveal the effect of flow time on stability and dimension of formed shish. It was found that the short flow time of 2 s was able to generate shish during flow, which, however, relaxed during the isothermal process after cessation of flow. An increase in flow time can improve the shish stability and the long flow time of 6 s can generate the stable shish that nucleate the growth of kebab lamellae. In addition, the quantitative analysis of SAXS results showed that with increasing flow time from 2 to 6 s, the shish length increased from 242 to 574 nm, while the shish diameter remained around 34 nm. This detailed information of the formed shish-kebab structure can be used to shed light on their evolution that occurred during flow from 2 to 6 s, where shish grew at a longitudinal speed of around 80 nm/s, and there was an improvement in the stability and nucleation capability for kebab lamellae.

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Microtubule nucleation sequence studied by time-resolved x-ray scattering and electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100077402 ◽

1983 ◽

Vol 41 ◽

pp. 766-767

Author(s):

Eva-Maria Mandelkow ◽

Eckhard Mandelkow ◽

Joan Bordas

Keyword(s):

Electron Microscopy ◽

Dynamic Equilibrium ◽

Time Resolved ◽

X Ray ◽

Additional Information ◽

X Ray Scattering ◽

Low Concentrations ◽

Microtubule Growth ◽

Ray Patterns ◽

Ray Scattering

When a solution of microtubule protein is changed from non-polymerising to polymerising conditions (e.g. by temperature jump or mixing with GTP) there is a series of structural transitions preceding microtubule growth. These have been detected by time-resolved X-ray scattering using synchrotron radiation, and they may be classified into pre-nucleation and nucleation events. X-ray patterns are good indicators for the average behavior of the particles in solution, but they are difficult to interpret unless additional information on their structure is available. We therefore studied the assembly process by electron microscopy under conditions approaching those of the X-ray experiment. There are two difficulties in the EM approach: One is that the particles important for assembly are usually small and not very regular and therefore tend to be overlooked. Secondly EM specimens require low concentrations which favor disassembly of the particles one wants to observe since there is a dynamic equilibrium between polymers and subunits.

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Characterisation of planar crystal defects in Y2Fe17Cx (0.6 ≤ x ≤ 1.6) magnetic material by High Resolution Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177003 ◽

1990 ◽

Vol 48 (4) ◽

pp. 774-775

Author(s):

W. Coene ◽

F. Hakkens ◽

T.H. Jacobs ◽

K.H.J. Buschow

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Permanent Magnets ◽

Annealing Treatment ◽

High Resolution Electron Microscopy ◽

Crystal Defects ◽

Ordered Structure ◽

X Ray ◽

Planar Crystal ◽

Resolution Electron

Intermetallic compounds of the type RE2Fe17Cx (RE= rare earth element) are promising candidates for permanent magnets. In case of Y2Fe17Cx, the Curie temperature increases from 325 K for x =0 to 550 K for x = 1.6 . X ray and electron diffraction reveal a carbon - induced structural transformation in Y2Fe17Cx from the hexagonal Th2Ni17 - type (x < 0.6 ) to the rhombohedral Th2Zn17 - type ( x ≥ 0.6). Planar crystal defects introduce local sheets of different magnetic anisotropy as compared with the ordered structure, and therefore may have an important impact on the coercivivity mechanism .High resolution electron microscopy ( HREM ) on a Philips CM30 / Super Twin has been used to characterize planar crystal defects in rhombohedral Y2Fe17Cx ( x ≥ 0.6 ). The basal plane stacking sequences are imaged in the [100] - orientation, showing an ABC or ACB sequence of Y - atoms and Fe2 - dumbbells, for both coaxial twin variants, respectively . Compounds resulting from a 3 - week annealing treatment at high temperature ( Ta = 1000 - 1100°C ) contain a high density of planar defects.

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Time-Resolved Cryo-Electron Microscopy of Oscillating Microtubules

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100181269 ◽

1990 ◽

Vol 48 (1) ◽

pp. 502-503

Author(s):

Eva-Maria Mandelkow ◽

Ron Milligan

Keyword(s):

Electron Microscopy ◽

Dynamic Instability ◽

Entire Solution ◽

Reaction Scheme ◽

Time Resolved ◽

X Ray ◽

X Ray Scattering ◽

A Chain ◽

Ray Scattering

Microtubules form part of the cytoskeleton of eukaryotic cells. They are hollow libers of about 25 nm diameter made up of 13 protofilaments, each of which consists of a chain of heterodimers of α-and β-tubulin. Microtubules can be assembled in vitro at 37°C in the presence of GTP which is hydrolyzed during the reaction, and they are disassembled at 4°C. In contrast to most other polymers microtubules show the behavior of “dynamic instability”, i.e. they can switch between phases of growth and phases of shrinkage, even at an overall steady state [1]. In certain conditions an entire solution can be synchronized, leading to autonomous oscillations in the degree of assembly which can be observed by X-ray scattering (Fig. 1), light scattering, or electron microscopy [2-5]. In addition such solutions are capable of generating spontaneous spatial patterns [6].In an earlier study we have analyzed the structure of microtubules and their cold-induced disassembly by cryo-EM [7]. One result was that disassembly takes place by loss of protofilament fragments (tubulin oligomers) which fray apart at the microtubule ends. We also looked at microtubule oscillations by time-resolved X-ray scattering and proposed a reaction scheme [4] which involves a cyclic interconversion of tubulin, microtubules, and oligomers (Fig. 2). The present study was undertaken to answer two questions: (a) What is the nature of the oscillations as seen by time-resolved cryo-EM? (b) Do microtubules disassemble by fraying protofilament fragments during oscillations at 37°C?

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