scholarly journals Method for Collecting Air-Water Interface Microbes Suitable for Subsequent Microscopy and Molecular Analysis in both Research and Teaching Laboratories

2004 ◽  
Vol 70 (4) ◽  
pp. 2486-2493 ◽  
Author(s):  
Margaret C. Henk
Keyword(s):  
Molecular Analysis ◽  
Bulk Water ◽  
Water Interface ◽  
Sampling Device ◽  
Force Microscopy ◽  
Research And Teaching ◽  
Transmission Electron ◽  
Air Water Interface ◽  
Culture Independent ◽  
Fluorescence Light

ABSTRACT A method has been developed for collecting air-water interface (AWI) microbes and biofilms that enables analysis of the same sample with various combinations of bright-field and fluorescence light microscopy optics, scanning and transmission electron microscopy (TEM), and atomic force microscopy. The identical sample is then subjected to molecular analysis. The sampling tool consists of a microscope slide supporting appropriate substrates, TEM grids, for example, that are removable for the desired protocols. The slide with its substrates is then coated with a collodion polymer membrane to which in situ AWI organisms adhere upon contact. This sampling device effectively separates the captured AWI bacterial community from the bulk water community immediately subtending. Preliminary data indicate that the AWI community differs significantly from the water column community from the same sample site when both are evaluated with microscopy and with 16S ribosomal DNA sequence-based culture-independent comparisons. This microbe collection method can be used at many levels in research and teaching.

scholarly journals Batch Production of High-Quality Graphene Grids for Cryo-EM: Cryo-EM Structure of Methylococcus capsulatus Soluble Methane Monooxygenase Hydroxylase

2021 ◽  
Author(s):  
Eungjin Ahn ◽  
byungchul Kim ◽  
uhn-soo Cho
Keyword(s):  
Protein Denaturation ◽  
Methane Monooxygenase ◽  
Atomic Layer ◽  
Water Interface ◽  
Methylococcus Capsulatus ◽  
Force Microscopy ◽  
Voltage Electron ◽  
Soluble Methane Monooxygenase ◽  
Air Water Interface ◽  
Scanning Em

Cryogenic electron microscopy (cryo-EM) has become a widely used tool for determining protein structure. Despite recent advances in instruments and algorithms, sample preparation remains a major bottleneck for several reasons, including protein denaturation at the air/water interface and the presence of preferred orientations and nonuniform ice layers. Graphene, a two-dimensional allotrope of carbon consisting of a single atomic layer, has recently attracted attention as a near-ideal support film for cryo-EM that can overcome these challenges because of its superior properties, including mechanical strength and electrical conductivity. Graphene minimizes background noise and provides a stable platform for specimens under a high-voltage electron beam and cryogenic conditions. Here, we introduce a reliable, easily implemented, and reproducible method of producing 36 graphene-coated grids at once within 1.5 days. The quality of the graphene grids was assessed using various tools such as scanning EM, Raman spectroscopy, and atomic force microscopy. To demonstrate their practical application, we determined the cryo-EM structure of Methylococcus capsulatus soluble methane monooxygenase hydroxylase (sMMOH) at resolutions of 2.9 and 2.4 angstrom using Quantifoil and graphene-coated grids, respectively. We found that the graphene-coated grid has several advantages; for example, it requires less protein, enables easy control of the ice thickness, and prevents pro-tein denaturation at the air/water interface. By comparing the cryo-EM structure of sMMOH with its crystal structure, we revealed subtle yet significant geometrical differences at the non-heme di-iron center, which may better indicate the active site configuration of sMMOH in the resting/oxidized state.

Structural and Morphological Characterization of Ultrathin Films of an Asymmetric Polydiacetylene

1996 ◽  
Vol 440 ◽  
Author(s):  
H. C. Wang ◽  
D. W. Cheong ◽  
J. Kumar ◽  
C. Sung ◽  
S. K. Tripathy
Keyword(s):  
Second Harmonic ◽  
Morphological Characterization ◽  
Lb Films ◽  
Force Microscopy ◽  
Langmuir Blodgett ◽  
Glass Substrates ◽  
Atomic Force ◽  
Transmission Electron ◽  
Air Water Interface

AbstractA soluble, asymmetrically substituted polydiacetylene, poly(BPOD), has been reported to form stable monolayers at the air-water interface by the Langmuir-Blodgett (LB) technique [2]. Preformed polydiacetylene has been deposited onto hydrophobic substrates as multilayers to form second order nonlinear optical thin films. Second harmonic generation was found to increase with the number of layers. From previous atomic force microscopy (AFM) studies backbone orientation along the dipping direction with an interchain spacing of about 5 A° was indicated [2].The film morphology and preferential molecular orientation of these LB films are further investigated by transmission electron microscopy (TEM). A specifically tailored sample preparation method for the ultrathin LB films was used. Multilayer films were deposited on hydrophobic collodion covered glass substrates for this purpose. Electron diffraction was employed to study the crystalline organization of mono and multilayers of LB films as well as cast films.

scholarly journals Aerosol microdroplets exhibit a stable pH gradient

2018 ◽  
Vol 115 (28) ◽  
pp. 7272-7277 ◽  
Author(s):  
Haoran Wei ◽  
Eric P. Vejerano ◽  
Weinan Leng ◽  
Qishen Huang ◽  
Marjorie R. Willner ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Bulk Water ◽  
Bulk Solution ◽  
Spatial Gradient ◽  
Water Interface ◽  
Atmospheric Reactions ◽  
Air Water Interface ◽  
Surface Enhanced Raman ◽  
Enhanced Raman Scattering ◽  
2D And 3D

Suspended aqueous aerosol droplets (<50 µm) are microreactors for many important atmospheric reactions. In droplets and other aquatic environments, pH is arguably the key parameter dictating chemical and biological processes. The nature of the droplet air/water interface has the potential to significantly alter droplet pH relative to bulk water. Historically, it has been challenging to measure the pH of individual droplets because of their inaccessibility to conventional pH probes. In this study, we scanned droplets containing 4-mercaptobenzoic acid–functionalized gold nanoparticle pH nanoprobes by 2D and 3D laser confocal Raman microscopy. Using surface-enhanced Raman scattering, we acquired the pH distribution inside approximately 20-µm-diameter phosphate-buffered aerosol droplets and found that the pH in the core of a droplet is higher than that of bulk solution by up to 3.6 pH units. This finding suggests the accumulation of protons at the air/water interface and is consistent with recent thermodynamic model results. The existence of this pH shift was corroborated by the observation that a catalytic reaction that occurs only under basic conditions (i.e., dimerization of 4-aminothiophenol to produce dimercaptoazobenzene) occurs within the high pH core of a droplet, but not in bulk solution. Our nanoparticle probe enables pH quantification through the cross-section of an aerosol droplet, revealing a spatial gradient that has implications for acid-base–catalyzed atmospheric chemistry.

scholarly journals Air–water interface of submerged superhydrophobic surfaces imaged by atomic force microscopy

2017 ◽  
Vol 8 ◽  
pp. 1671-1679 ◽  
Author(s):  
Markus Moosmann ◽  
Thomas Schimmel ◽  
Wilhelm Barthlott ◽  
Matthias Mail
Keyword(s):  
Atomic Force Microscopy ◽  
Current Knowledge ◽  
Biological Species ◽  
Optical Methods ◽  
Water Interface ◽  
Contact Mode ◽  
Structured Surfaces ◽  
Force Microscopy ◽  
Atomic Force ◽  
Air Water Interface

Underwater air retention of superhydrophobic hierarchically structured surfaces is of increasing interest for technical applications. Persistent air layers (the Salvinia effect) are known from biological species, for example, the floating fern Salvinia or the backswimmer Notonecta. The use of this concept opens up new possibilities for biomimetic technical applications in the fields of drag reduction, antifouling, anticorrosion and under water sensing. Current knowledge regarding the shape of the air–water interface is insufficient, although it plays a crucial role with regards to stability in terms of diffusion and dynamic conditions. Optical methods for imaging the interface have been limited to the micrometer regime. In this work, we utilized a nondynamic and nondestructive atomic force microscopy (AFM) method to image the interface of submerged superhydrophobic structures with nanometer resolution. Up to now, only the interfaces of nanobubbles (acting almost like solids) have been characterized by AFM at these dimensions. In this study, we show for the first time that it is possible to image the air–water interface of submerged hierarchically structured (micro-pillars) surfaces by AFM in contact mode. By scanning with zero resulting force applied, we were able to determine the shape of the interface and thereby the depth of the water penetrating into the underlying structures. This approach is complemented by a second method: the interface was scanned with different applied force loads and the height for zero force was determined by linear regression. These methods open new possibilities for the investigation of air-retaining surfaces, specifically in terms of measuring contact area and in comparing different coatings, and thus will lead to the development of new applications.

Molecular dynamics simulations predict an accelerated dissociation of H2CO3 at the air–water interface

2014 ◽  
Vol 16 (46) ◽  
pp. 25573-25582 ◽  
Author(s):  
Mirza Galib ◽  
Gabriel Hanna
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Carbonic Acid ◽  
Bulk Water ◽  
Water Interface ◽  
Air Water Interface ◽  
Dynamics Simulations ◽  
Dissociation Barrier

Ab initio molecular dynamics simulations of carbonic acid (H2CO3) at the air–water interface yield a lower dissociation barrier than in bulk water.

scholarly journals Interfacial Interactions and Nanostructure Changes in DPPG/HD Monolayer at the Air/Water Interface

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Huaze Zhu ◽  
Runguang Sun ◽  
Tao Zhang ◽  
Changchun Hao ◽  
Pengli Zhang ◽  
...  
Keyword(s):  
Lung Surfactant ◽  
Compression Modulus ◽  
Metabolic Energy ◽  
Excess Gibbs Free Energy ◽  
Valuable Insight ◽  
Water Interface ◽  
Force Microscopy ◽  
Lung Expansion ◽  
Air Water Interface ◽  
Pressure Area

Lung surfactant (LS) plays a crucial role in regulating surface tension during normal respiration cycles by decreasing the work associated with lung expansion and therefore decreases the metabolic energy consumed. Monolayer surfactant films composed of a mixture of phospholipids and spreading additives are of optional utility for applications in lung surfactant-based therapies. A simple, minimal model of such a lung surfactant system, composed of 1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-(1-gylcerol)] (DPPG) and hexadecanol (HD), was prepared, and the surface pressure-area (π-A) isotherms and nanostructure characteristics of the binary mixture were investigated at the air/water interface using a combination of Langmuir-Blodgett (LB) and atomic force microscopy (AFM) techniques. Based on the regular solution theory, the miscibility and stability of the two components in the monolayer were analyzed in terms of compression modulus (Cs-1) , excess Gibbs free energy (ΔGexcπ) , activity coefficients (γ), and interaction parameter (ξ). The results of this paper provide valuable insight into basic thermodynamics and nanostructure of mixed DPPG/HD monolayers; it is helpful to understand the thermodynamic behavior of HD as spreading additive in LS monolayer with a view toward characterizing potential improvements to LS performance brought about by addition of HD to lung phospholipids.

Imaging Phospholipid Arrangement in Pultonary Surfactant Using Atomic Force Microscopy

2000 ◽  
Vol 6 (S2) ◽  
pp. 870-871
Author(s):  
K. Nag ◽  
F. Possmayer ◽  
N. O. Petersen ◽  
S. A. Hearn
Keyword(s):  
Surface Tension ◽  
Lung Surfactant ◽  
Water Interface ◽  
Force Microscopy ◽  
Atomic Force ◽  
Alveolar Collapse ◽  
Air Water Interface ◽  
Associated Proteins ◽  
Gel Phase ◽  
Gel Transition

Lung surfactant stabilizes the pulmonary air-water interface, by enriching this interface with films of amphipathic phospholipids. These films reduce the surface tension of the air-water interface to very low values (∼ 1 mN/m) at end expiration and prevents alveolar collapse. Surfactant contains mainly phospholipids (90%), and small amounts of associated proteins. Among the phospholipids, saturated dipalmitoylphosphatidylcholine (DPPC) and monounsaturated phosphatidylcholine are the main surfactant components, although significant amounts of other lipids are also present (1). DPPC is the only component of surfactant which exists in gel phase at physiological temperature, films of which can reduce the air-water surface tension to low values. DPPC films can undergo a fluid to gel transition with increase in the molecular packing leading to superstructures or domains (2). However it is not clear how the molecules of surfactant pack at the air-water interface to form highly compact films, and if DPPC phase segregate in such films.

scholarly journals Self-Assembly Properties of Amphiphilic Iron(III) Spin Crossover Complexes in Water and at the Air–Water Interface

2018 ◽  
Vol 4 (4) ◽  
pp. 49 ◽  
Author(s):  
Paulo N. Martinho ◽  
Irina A. Kühne ◽  
Brendan Gildea ◽  
George McKerr ◽  
Barry O’Hagan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
Spin Crossover ◽  
Water Soluble ◽  
Water Interface ◽  
Nanoparticle Formation ◽  
Alkyl Chains ◽  
Transmission Electron ◽  
Air Water Interface ◽  
Magnetic Profile

The assembly properties of three known spin crossover iron(III) complexes 1–3, at the air–water interface, are reported. All three complexes are amphiphiles, each bearing a pair of Cn alkyl chains on the polyamino Schiff base sal2trien ligand (n = 6, 12, or 18). Complex 1 is water-soluble but complexes 2 and 3 form Langmuir films, and attempts were made to transfer the film of the C18 complex 3 to a glass surface. The nature of the assembly of more concentrated solutions of 3 in water was investigated by light scattering, cryo-SEM (scanning electron microscopy), and TEM (transmission electron microscopy), all of which indicated nanoparticle formation. Lyophilization of the assembly of complex 3 in water yielded a powder with a markedly different magnetic profile from the powder recovered from the initial synthesis, notably, the spin crossover was almost completely quenched, and the thermal behavior was predominantly low spin, suggesting that nanoparticle formation traps the system in one spin state.

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