Ultrafast Dynamics at Lipid-Water Interfaces.

Lipid membranes are more than just barriers between cell compartments; they provide molecular environments with a finely tuned balance between hydrophilic and hydrophobic interactions that enable proteins to dynamically fold and self-assemble to regulate biological function. Characterizing dynamics at the lipid-water interface is essential to understanding molecular complexities from the thermodynamics of liquid-liquid phase separation down to picosecond-scale reorganization of interfacial hydrogen-bond networks.Ultrafast vibrational spectroscopy, including two-dimensional infrared (2D IR) and vibrational sum-frequency generation (VSFG) spectroscopies, is a powerful tool to examine picosecond interfacial dynamics.

Ultrafast Spectroscopy of Lipid-Water Interfaces: Transmembrane Crowding Drives H-Bond Dynamics.

Biology takes place in crowded, heterogeneous environments, and it is therefore essential to account for crowding effects in our understanding of biophysical processes at the molecular level. Comparable to the cytosol, proteins occupy approximately 30% of the plasma membrane surface; thus, crowding should have an effect on the local structure and dynamics at the lipid-water interface. Using a combination of ultrafast two-dimensional infrared spectroscopy and molecular dynamics simulations, we quantify the effects of membrane peptide concentration on the picosecond interfacial H-bond dynamics.

Liquid-Liquid Phase Separation Produces Fast H-Bond Dynamics in DMSO-Water Mixtures.

Liquid-liquid phase separation is common in complex mixtures, but the behavior of nanoconfined liquids is poorly understood from a physical perspective. Dimethyl sulfoxide (DMSO) is an amphiphilic molecule with unique concentration-dependent bulk properties in mixtures with water. Here, we use ultrafast two-dimensional infrared (2D IR) spectroscopy to measure the H-bond dynamics of two probe molecules with different polarities: formamide (FA) and dimethylformamide (DMF).

Ultrafast pH-jump two-dimensional infrared spectroscopy.

We present a pH-jump two-dimensional infrared (2D IR) spectrometer to probe pH-dependent conformational changes from nanoseconds to milliseconds. The design incorporates a nanosecond 355 nm source into a pulse-shaper-based 2D IR spectrometer to trigger dissociation of a caged proton prior to probing subsequent conformational changes with femtosecond 2D IR spectroscopy. We observe a blue shift in the amide I mode (C═O stretch) of diglycine induced by protonation of the terminal amine.

Imaging and the Lung Transplant Patient.

Lung transplantation can prolong and improve quality of life for patients affected by end-stage lung disease. Potential lung transplant patients undergo a rigorous preoperative assessment that includes multiple medical imaging studies. These studies provide information that help physicians determine whether the patient is a surgical candidate, as well as the surgical technique that should be used during transplantation.

Site-Specific Peptide Probes Detect Buried Water in a Lipid Membrane.

Transmembrane peptides contain polar residues in the interior of the membrane, which may alter the electrostatic environment and favor hydration in the otherwise nonpolar environment of the membrane core. Here, we demonstrate a general, nonperturbative strategy to probe hydration of the peptide backbone at specific depths within the bilayer using a combination of site-specific isotope labels, ultrafast two-dimensional infrared spectroscopy, and spectral modeling based on molecular dynamics simulations. Our results show that the amphiphilic pH-low insertion peptide supports a highly heterogeneous environment, with significant backbone hydration of nonpolar residues neighboring charged residues.

Fluoroscopic Evaluation of Adult Male Urethral Abnormalities.

Retrograde urethrograms and voiding cystourethrograms provide clinicians with important information to determine treatment options and surgical interventions for patients with urethral abnormalities. This article discusses the elements with which radiologic technologists should be familiar, including urethra anatomy, the pathology of urethral abnormalities, imaging techniques, and special considerations for preoperative and postoperative patients.

An Empirical IR Frequency Map for Ester C═O Stretching Vibrations.

We present an approach for parametrizing spectroscopic maps of carbonyl groups against experimental IR absorption spectra. The model correlates electric fields sampled from molecular dynamics simulations with vibrational frequencies and line shapes in different solvents. We perform an exhaustive search of parameter combinations and optimize the parameter values for the ester carbonyl stretching mode in ethyl acetate by comparing to experimental FTIR spectra of the small molecule in eight different solvents of varying polarities.

Esophagectomy and Gastric Pull-through Procedures: Surgical Techniques, Imaging Features, and Potential Complications.

Esophagectomy takes the center stage in the curative treatment of local and local-regional esophageal cancer. It is a complex procedure with a high postoperative complication rate. When interpreting imaging studies, radiologists must understand the surgical techniques used and their potential complications.

Porphyrobacter mercurialis sp. nov., isolated from a stadium seat and emended description of the genus Porphyrobacter.

A novel, Gram-negative, non-spore-forming, pleomorphic yellow-orange bacterial strain was isolated from a stadium seat. Strain Coronado(T) falls within the Erythrobacteraceae family and the genus Porphyrobacter based on 16S rRNA phylogenetic analysis. This strain has Q-10 as the predominant respiratory lipoquinone, as do other members of the family.

Draft Genome Sequence of Curtobacterium flaccumfaciens Strain UCD-AKU (Phylum Actinobacteria).

Here we present the draft genome of an actinobacterium, Curtobacterium flaccumfaciens strain UCD-AKU, isolated from a residential carpet. The genome assembly contains 3,692,614 bp in 130 contigs. This is the first member of the Curtobacterium genus to be sequenced.