No abstract

No abstract

By adding a small amount of a vesicle surfactant, “unavoidable” splashing is considerably reduced on superhydrophobic surfaces.

We previously reported that the protonation state of the carboxyl group of amino acids and peptides in the solid state can easily be determined by the carbon chemical shielding tensors but not by the isotropic shifts. In this report the substantial variation in the 22 element for both protonated and deprotonated forms is shown to be a result of hydrogen bonding. We have correlated this tensor element with established measures of hydrogen bonding, namely the IR stretching frequencies of the carbonyl and the asymmetric stretching frequency for the protonated and deprotonated carboxy groups, respectively. We also observed a strong correlation between the 22 values and previously reported O-H hydrogen bonding distances from the carbonyl of protonated acids to the nearest proton donor. In the database, we found a fixed geometry for the protonated acids and a variable and complicated geometry for hydrogen bond interaction in deprotonated carboxylate. Correspondingly, the correlation betweeen NMR, IR, and diffraction data is more convincing for the protonated acids.

Wearable biosensors as a user-friendly measurement platform have become a rapidly growing field of interests due to their possibility in integrating traditional medical diagnostics and healthcare management into miniature lab-on-body analytic devices. This paper demonstrates a flexible and skin-mounted band that combines superhydrophobic-superhydrophilic microarrays with nanodendritic colorimetric biosensors toward in situ sweat sampling and analysis. Particularly, on the superwettable bands, the superhydrophobic background could confine microdroplets into superhydrophilic microwells. On-body investigations further reveal that the secreted sweat is repelled by the superhydrophobic silica coating and precisely collected and sampled onto the superhydrophilic micropatterns with negligible lateral spreading, which provides an independent “vessel” toward cellphone-based sweat biodetection (pH, chloride, glucose and calcium). Such wearable, superwettable band-based biosensors with improved interface controllability could significantly enhance epidemical sweat sampling in well-defined sites, holding a great promise for facile and noninvasive biofluids analysis.

In nature, many organisms are able to accommodate a complex living environment by developing biological wet adhesive surfaces with unique functions such as fixation and predation. Significantly, most of these outstanding functions originate from the specialized micro/nanostructures and/or chemical components of these natural organisms. To design artificial surfaces with remarkable wet adhesive properties, the underlying mechanisms of the fascinating adhesion phenomena are further explored and summarized to provide continuous inspiration. Herein, a systematic overview of biological wet adhesive surfaces and the corresponding artificial counterparts from the perspective of surface micro/nanostructures is provided. First, the research progress of the typical biological wet adhesive surfaces such as the octopus, tree frogs, and mayfly larvae is introduced. Then, the fundamental models of surface adhesion in natural organisms and the commonly used instruments for measuring adhesion force are discussed. Later, the corresponding artificial wet adhesive surfaces inspired by these representative organisms are highlighted. After that, the typical methods for fabricating these surfaces are briefly introduced. Finally, future challenges and opportunities to develop bioinspired multiscaled wet adhesive surfaces with controlled adhesion are presented.

Solid state 13C−1H 2D HETeronuclear CORrelation spectra (Caravatti, P.; Bodenhausen, G.; Ernst, R. R. Chem. Phys. Lett. 1982, 89, 363−367. Roberts, J. E.; Vega, S.; Griffin, R. G. J. Am. Chem. Soc. 1984, 106, 2506−2512) are reported for many amino acids and peptides with 13C isotopic composition at natural abundance. These HETCOR spectra often have multiple proton cross peaks for each carbon, and these cross peaks can be extremely helpful for assigning the spectrum. Apart from peaks due to groups that have a lot of motion, the peak volumes correlate with C−H distance and can be used to estimate distances with standard derivation of 0.2 Å; the longest distances for which cross peaks are visible is 3 Å. The HECTOR pulse sequence also appears to be very useful for studying hydrogen bonding interactions, since the distances for most of C−O···H−X hydrogen bond pairs are within the range that is observable by HETCOR.

No abstract