Rigid Double-Stranded DNA Linkers for Single Molecule Enzyme-Drug Interaction Measurements Using Molecular Recognition Force Spectroscopy.

Single-molecule studies can reveal the distribution of states and interactions between ligand-enzyme complexes not accessible for most studies that measure a large ensemble average response of many molecules. Furthermore, in some biological applications, the information regarding the outliers, not the average of measured properties, can be more important. The high spatial and force resolution provided by atomic force microscopy (AFM) under physiological conditions has been utilized in this study to quantify the force-distance relations of enzyme-drug interactions.

Direct Surface Tension Measurements of Individual Sub-Micrometer Particles Using Atomic Force Microscopy.

Understanding the role of sea spray aerosol (SSA) on climate and the environment is of great interest due to their high number concentration throughout the Earth's atmosphere. Despite being of fundamental importance, direct surface tension measurements of SSA relevant sub-micrometer particles are rare, largely due to their extremely small volumes. Herein, atomic force microscopy (AFM) is used to directly measure the surface tension of individual sub-micrometer SSA particle mimics at ambient temperature and varying relative humidity (RH).

Linking hygroscopicity and the surface microstructure of model inorganic salts, simple and complex carbohydrates, and authentic sea spray aerosol particles.

Individual airborne sea spray aerosol (SSA) particles show diversity in their morphologies and water uptake properties that are highly dependent on the biological, chemical, and physical processes within the sea subsurface and the sea surface microlayer. In this study, hygroscopicity data for model systems of organic compounds of marine origin mixed with NaCl are compared to data for authentic SSA samples collected in an ocean-atmosphere facility providing insights into the SSA particle growth, phase transitions and interactions with water vapor in the atmosphere. In particular, we combine single particle morphology analyses using atomic force microscopy (AFM) with hygroscopic growth measurements in order to provide important insights into particle hygroscopicity and the surface microstructure.

The Impact of Aerosol Particle Mixing State on the Hygroscopicity of Sea Spray Aerosol.

Aerosol particles influence global climate by determining cloud droplet number concentrations, brightness, and lifetime. Primary aerosol particles, such as those produced from breaking waves in the ocean, display large particle-particle variability in chemical composition, morphology, and physical phase state, all of which affect the ability of individual particles to accommodate water and grow into cloud droplets. Despite such diversity in molecular composition, there is a paucity of methods available to assess how particle-particle variability in chemistry translates to corresponding differences in aerosol hygroscopicity.

Quantifying the Hygroscopic Growth of Individual Submicrometer Particles with Atomic Force Microscopy.

The water uptake behavior of atmospheric aerosol dictates their climate effects. In many studies, aerosol particles are deposited onto solid substrates to measure water uptake; however, the effects of the substrate are not well understood. Furthermore, in some cases, methods used to analyze and quantify water uptake of substrate deposited particles use a two-dimensional (2D) analysis to monitor growth by following changes in the particle diameter with relative humidity (RH).

Substrate-Deposited Sea Spray Aerosol Particles: Influence of Analytical Method, Substrate, and Storage Conditions on Particle Size, Phase, and Morphology.

Atmospheric aerosols are often collected on substrates and analyzed weeks or months after the initial collection. We investigated how the selection of substrate and microscopy method influence the measured size, phase, and morphology of sea spray aerosol (SSA) particles and how sample storage conditions affect individual particles using three common microscopy techniques: optical microscopy, atomic force microscopy, and scanning electron microscopy. Micro-Raman spectroscopy was used to determine changes in the water content of stored particles.

Correction: Humidity-dependent surface tension measurements of individual inorganic and organic submicrometre liquid particles.

[This corrects the article DOI: 10.1039/C4SC03716B.].

Humidity-dependent surface tension measurements of individual inorganic and organic submicrometre liquid particles.

Surface tension, an important property of liquids, is easily measured for bulk samples. However, for droplets smaller than one micron in size, there are currently no reported measurements. In this study, atomic force microscopy (AFM) and force spectroscopy have been utilized to measure surface tension of individual submicron sized droplets at ambient pressure and controlled relative humidity (RH).

Size matters in the water uptake and hygroscopic growth of atmospherically relevant multicomponent aerosol particles.

Understanding the interactions of water with atmospheric aerosols is crucial for determining the size, physical state, reactivity, and climate impacts of this important component of the Earth's atmosphere. Here we show that water uptake and hygroscopic growth of multicomponent, atmospherically relevant particles can be size dependent when comparing 100 nm versus ca. 6 μm sized particles.