Microsolvation Of The Green Fluorescent Protein Chromophore One Water Molecule At A Time

Solvation plays an important role in the function of fluorescent proteins. Many of these proteins contain a functional water molecule in the chromophore pocket, which can influence the electronic properties of the chromophore. In the case of the Green Fluorescent Protein (GFP), a single water molecule is coordinated to the phenolate group of the chromophore, raising questions about the effect this has on the electronic spectrum of GFP. Here, we present the electronic and infrared spectra of a model system for the GFP chromophore in complexes with up to two water molecules

The electronic spectrum of cryogenic ruthenium-tris-bipyridine dications

We present the electronic spectrum of Ru(II)-tris(2,2’-bipyridine), Ru(bpy)$_3^{2+}$, measured by photodissociation spectroscopy of mass selected Ru(bpy)$_3^{2+}\cdot$N$_2$ ions prepared in a cryogenic quadrupole ion trap. The spectrum is composed of several metal-to-ligand charge transfer (MLCT) transitions, as well as metal centered bands and ligand centered \pi \pi^ states. We observe several partially resolved electronic transitions in the MLCT band. We discuss the results in the framework of time-dependent density functional theory

ELECTRONIC PHOTODISSOCIATION SPECTROSCOPY OF COLD NITROPHENOLATE IONS. PART II. META-NITROPHENOLATE

Isomers of nitrophenolate can serve as models for flourophores commonly found in fluorescent proteins. Here we report electronic spectra for mass-selected 3-nitrophenolate ions prepared in a cryogenic ion trap, measured by photodissociation spectroscopy. Different from the two other isomers, the spectrum shows sharp vibrational bands at low temperatures. We present a Franck-Condon analysis of the spectrum, and discuss the differences between the spectra of the different isomers

ELECTRONIC AND INFRARED PHOTODISSOCIATION SPECTROSCOPY OF PROTOPORPHYRIN IN VACUO

Porphyrins are ubiquitous macrocycles in biology, where they perform a variety of functions ranging from behaving as chromophores in proteins to molecular/electron shuttles. Porphyrins often incorporate a metal center and have substituents on the macrocycle periphery to allow this versatility. These species have been studied for decades, using many techniques primarily focused on solution and solid phase environments. While such techniques yield much useful information, the chemical environment and the temperatures involved in such studies usually lead to solvatochromic shifts, broadening of spectral lines, and spectral congestion. Even spectra obtained in cryogenic matrices exhibit shifts whose magnitude and even direction are hard to predict. As a consequence, the intrinsic photophysical properties of these molecules, i.e., in the absence of effects caused by chemical environments, have been elusive. We are able to circumvent these difficulties by studying cryogenically prepared, mass selected ions. Here we report the electronic and infrared spectra of metal free protoporphyrin mono- and dianions. We interpret the experimental data in the framework of quantum chemical calculations

HEAVY ATOM VIBRATIONAL MODES AND LOW-ENERGY VIBRATIONAL AUTODETACHMENT IN NITROMETHANE ANIONS

We use Ar predissociation and vibrational autodetachment below 2100 wn to obtain vibrational spectra of the low-energy modes of nitromethane anion. We interpret the spectra using anharmonic calculations, which reveal strong mode coupling and Fermi resonances. Not surprisingly, the number of evaporated Ar atoms varies with photon energy, and we follow the propensity of evaporating two versus one Ar atoms as photon energy increases. The photodetachment spectrum is discussed in the context of threshold effects and the importance of hot bands

CHARGE OSCILLATION IN C−O STRETCHING VIBRATIONS: A COMPARISON OF CO2− ANION AND CARBOXYLATE FUNCTIONAL GROUPS

We compare the intensity ratio of symmetric to antisymmetric C$-$O stretching vibrational transitions in CO$_2^-$ and MCOO$^-$ (M = H, Ag and Bi) using photodissociation spectroscopy. This ratio depends strongly on the bonding partner M, caused by a dynamic change in the molecular charge distribution during vibrational motion. Density functional theory calculations indicate that such charge oscillations can occur for both the symmetric and antisymmetric C$-$O stretching vibrations in these systems. In the symmetric C$-$O stretching modes, however, they are at play only if a bonding partner is present, which acts as a reservoir for charge during CO bond compression in the symmetric stretching vibration

Hepatocyte apoptosis is tumor promoting in murine nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease is the most common chronic liver disease and may progress to nonalcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC). The molecular determinants of this pathogenic progression, however, remain largely undefined. Since liver tumorigenesis is driven by apoptosis, we examined the effect of overt hepatocyte apoptosis in a mouse model of NASH using mice lacking myeloid cell leukemia 1 (Mcl1), a pro-survival member of the BCL-2 protein family. Hepatocyte-specific Mcl1 knockout (Mcl1$^{∆hep}$) mice and control littermates were fed chow or FFC (high saturated fat, fructose, and cholesterol) diet, which induces NASH, for 4 and 10 months. Thereafter, liver injury, inflammation, fibrosis, and tumor development were evaluated biochemically and histologically. Mcl1$^{∆hep}$ mice fed with the FFC diet for 4 months displayed a marked increase in liver injury, hepatocyte apoptosis, hepatocyte proliferation, macrophage-associated liver inflammation, and pericellular fibrosis in contrast to chow-fed Mcl1$^{∆hep}$ and FFC diet-fed Mcl1-expressing littermates. After 10 months of feeding, 78% of FFC diet-fed Mcl1$^{∆hep}$ mice developed liver tumors compared to 38% of chow-fed mice of the same genotype. Tumors in FFC diet-fed Mcl1$^{∆hep}$ mice were characterized by cytologic atypia, altered liver architecture, immunopositivity for glutamine synthetase, and histologically qualified as HCC. In conclusion, this study provides evidence that excessive hepatocyte apoptosis exacerbates the NASH phenotype with enhancement of tumorigenesis in mice

Small Things Matter: Relevance of MicroRNAs in Cardiovascular Disease

MicroRNAs (miRNAs) are short sequences of non-coding RNA that play an important role in the regulation of gene expression and thereby in many physiological and pathological processes. Furthermore, miRNAs are released in the extracellular space, for example in vesicles, and are detectable in various biological fluids, such as serum, plasma, and urine. Over the last years, it has been shown that miRNAs are crucial in the development of several cardiovascular diseases (CVDs). This review discusses the (patho)physiological implications of miRNAs in CVD, ranging from cardiovascular risk factors (i.e., hypertension, diabetes, dyslipidemia), to atherosclerosis, myocardial infarction, and cardiac remodeling. Moreover, the intriguing possibility of their use as disease-specific diagnostic and prognostic biomarkers for human CVDs will be discussed in detail. Finally, as several approaches have been developed to alter miRNA expression and function (i.e., mimics, antagomirs, and target-site blockers), we will highlight the miRNAs with the most promising therapeutic potential that may represent suitable candidates for therapeutic intervention in future translational studies and ultimately in clinical trials. All in all, this review gives a comprehensive overview of the most relevant miRNAs in CVD and discusses their potential use as biomarkers and even therapeutic targets

The effects of water and microstructure on the performance of polymer electrolyte fuel cells

n this paper, we present a comprehensive non-isothermal, one-dimensional model of the cathode side of a Polymer Electrolyte Fuel Cell. We explicitly include the catalyst layer, gas diffusion layer and the membrane. The catalyst layer and gas diffusion layer are characterized by several measurable microstructural parameters. We model all three phases of water, with a view to capturing the effect that each has on the performance of the cell. A comparison with experiment is presented, demonstrating excellent agreement, particularly with regard to the effects of water activity in the channels and how it impacts flooding and membrane hydration. We present several results pertaining to the effects of water on the current density (or cell voltage), demonstrating the role of micro-structure, liquid water removal from the channel, water activity, membrane and gas diffusion layer thickness and channel temperature. These results provide an indication of the changes that are required to achieve optimal performance through improved water management and MEA-component design. Moreover, with its level of detail, the model we develop forms an excellent basis for a multi-dimensional model of the entire membrane electrode assembly