University of Rhode Island

About: University of Rhode Island is a education organization based out in Kingston, Rhode Island, United States. It is known for research contribution in the topics: Population & Bay. The organization has 11464 authors who have published 22770 publications receiving 841066 citations. The organization is also known as: URI & Rhode Island College of Agriculture and the Mechanic Arts.

Distribution of biogenic silica and quartz in recent deep-sea sediments

Abstract: All available quartz and biogenic silica concentrations from deep-sea surface sediments were intercalibrated, plotted, and contoured on a calcium-carbonate-free basis. The maps show highest concentrations of biogenic silica (opal) along the west African coast, along equatorial divergences in all oceans, and at the Polar Front in the southern Indian Ocean. These are all areas where upwelling is strong and there is high biological productivity. Quartz in pelagic sediments deposited far from land is generally eolian in origin. Its distribution reflects dominant wind systems in the Pacific, but in much of the Atlantic and Indian oceans the distribution pattern is strongly modified by turbidite deposition and bottom current processes.

Cell-penetrating homochiral cyclic peptides as nuclear-targeting molecular transporters.

Abstract: The intracellular delivery of biologically active cargos by employing linear cell-penetrating peptides (CPPs) has been previously reported. Conjugation to linear cationic CPPs, such as TAT (trans-acting activator of transcription; a peptide derived from the HIV-1 transactivator protein), 3] penetratin, antennapedia, or oligoarginine, efficiently enhances the cellular uptake through different mechanisms. The cellular uptake and internalization of many CPPs along with the conjugated cargo occurs predominantly by an endocytic pathway that involves macropinocytosis, a caveolae pathway, clathrin-mediated endocytosis, or lipid-raft dependent endocytosis. Endosomal uptake represents a major challenge in targeted intracellular drug delivery since some compounds are trapped in endosomes and cannot reach the biological targets in the cytoplasm or nucleus. Thus, strategies that promote endosomal escape or avoid endosomal routes are required for improving bioavailability. Moreover, the nuclear delivery of cell-impermeable and water-insoluble molecules remains a major challenge. The nucleus is a desirable target because the genetic information of the cell and transcription machinery resides there. To date, most approaches for nuclear delivery of compounds have taken advantage of covalent conjugation, which requires release of the cargo from the conjugate and/or endosomal escape. There is therefore a need to develop alternative stable peptide carriers that avoid endosomal pathways and/or covalent conjugation. Compared to linear peptides that are susceptible to hydrolysis by endogenous peptidases, cyclic peptides are enzymatically more stable. The cell-penetrating properties and application of homochiral l-cyclic peptides in drug delivery remain unexplored. Previous studies on linear CPPs by our research group and others indicated that an optimal balance of positive charge and hydrophobicity is required for interactions with the cell membrane and deep penetration into the lipid bilayer. 4,8–10] Herein, we report the design and evaluation of amphipathic homochiral l-cyclic peptides for potential applications as CPPs and/or as molecular transporters of bioactive compounds. Eleven cyclic peptides, namely [WR]4, [FK]4, [AK]4, [EL]4, [RFEF]2, [EK]4, [ER]4, [FR]4, [RFE]3, [WR]3, and [WR]5 (Scheme 1), which contain l-amino acids, were synthesized by employing 9-fluorenylmethyloxycarbonyl (Fmoc) based peptide chemistry. The selection of the cyclic peptides was based on the presence of hydrophobic residues (e.g., W, F, L) and charged residues (e.g., K, R, E). We hypothesized that an optimal amphipathic cyclic peptide that contains appropriate residues, and that undergoes intermolecular and intramolecular interactions can act as a CPP and/or entrap and deliver a bioactive compound intracellularly. To examine the potential application of the cyclic peptides as molecular transporters, a model experiment was performed with lamivudine (( )-2’,3’-dideoxy-3’-thiacytidine, 3TC). 3TC is a nucleoside reverse transcriptase inhibitor that blocks HIV-1 and hepatitis B virus replication. The efficient cellular uptake of 3TC is critical for effective antiviral activity. To monitor the molecular transport ability of the cyclic peptides, a carboxyfluorescein derivative of 3TC (F-3TC) was synthesized. The cellular uptake of the fluorescently labeled 3TC (F3TC) was examined in the leukemia CCRF-CEM cell line in the presence or absence of cyclic peptides. After 1 h incubation at 37 8C, the cells were treated with trypsin to remove the cell-surface-bound drug. The cellular uptake of F3TC was monitored by fluorescence-activated cell sorting (FACS; Figure 1a) and fluorescence microscopy (Figure 1b). The cyclic peptides did not exhibit any cytotoxicity by using an MTT assay at an experimental concentration of 50 mm in four different cell lines, namely CCRF-CEM, HT-29, MDAMD-468, and SK-OV-3, thus showing consistent results (Figure S12). FACS and fluorescence microscopy showed significantly higher fluorescence signals in the cells treated with F-3TCloaded [WR]4 and [WR]5 compared to those treated with other F-3TC-loaded cyclic peptides and with F-3TC alone, thus suggesting that the uptake of F-3TC is facilitated by [WR]n (n = 4, 5) and is dependent on nature of amino acids. F3TC-loaded [WR]5 exhibited a cellular uptake that was approximately five times higher than that of F-3TC alone (Figure 1a). Phosphopeptides are valuable probes for studying phosphoprotein–protein interactions because these peptides mimic the interactions between the negatively charged phosphate group of phosphoproteins and positively charged amino acids in the binding pockets of a number of proteins. Studying negatively charged phosphopeptides in cellular systems is challenging because these peptides do not readily [*] Dr. D. Mandal, A. Nasrolahi Shirazi, Prof. K. Parang Department of Biomedical and Pharmaceutical Sciences University of Rhode Island 41 Lower College Road, Kingston, RI 02881 (USA) E-mail: kparang@uri.edu

Abrupt change in tropical African climate linked to the bipolar seesaw over the past 55,000 years

Abstract: [1] The tropics play a major role in global climate dynamics, and are vulnerable to future climate change. We present a record of East African climate since 55 ka, preserved in Lake Malawi sediments, that indicates rapid shifts between discrete climate modes related to abrupt warming (D-O) events observed in Greenland. Although the timing of the Malawi events cannot be determined exactly, our age model implies that they occur prior to their Greenland counterparts, consistent with southward excursions of the Intertropical Convergence Zone during Greenland stadials. The magnitude of each of the events recorded in Malawi sediments corresponds to the scale of the subsequent Greenland warming. This suggests that a tropical component of climate sets a template for abrupt high northern latitude climate fluctuations associated with the bipolar seesaw.

Formaldehyde Distribution over North America: Implications for Satellite Retrievals of Formaldehyde Columns and Isoprene Emission

Abstract: Formaldehyde (HCHO) columns measured from space provide constraints on emissions of volatile organic compounds (VOCs). Quantitative interpretation requires characterization of errors in HCHO column retrievals and relating these columns to VOC emissions. Retrieval error is mainly in the air mass factor (AMF) which relates fitted backscattered radiances to vertical columns and requires external information on HCHO, aerosols, and clouds. Here we use aircraft data collected over North America and the Atlantic to determine the local relationships between HCHO columns and VOC emissions, calculate AMFs for HCHO retrievals, assess the errors in deriving AMFs with a chemical transport model (GEOS-Chem), and draw conclusions regarding space-based mapping of VOC emissions. We show that isoprene drives observed HCHO column variability over North America; HCHO column data from space can thus be used effectively as a proxy for isoprene emission. From observed HCHO and isoprene profiles we find an HCHO molar yield from isoprene oxidation of 1.6 +/- 0.5, consistent with current chemical mechanisms. Clouds are the primary error source in the AMF calculation; errors in the HCHO vertical profile and aerosols have comparatively little effect. The mean bias and 1Q uncertainty in the GEOS-Chem AMF calculation increase from <1% and 15% for clear skies to 17% and 24% for half-cloudy scenes. With fitting errors, this gives an overall 1 Q error in HCHO satellite measurements of 25-31%. Retrieval errors, combined with uncertainties in the HCHO yield from isoprene oxidation, result in a 40% (1sigma) error in inferring isoprene emissions from HCHO satellite measurements.

Coastal ecosystems: a critical element of risk reduction

Abstract: The conservation of coastal ecosystems can provide considerable coastal protection benefits, but this role has not been sufficiently accounted for in coastal planning and engineering. Substantial evidence now exists showing how, and under what conditions, ecosystems can play a valuable function in wave and storm surge attenuation, erosion reduction, and in the longer term maintenance of the coastal profile. Both through their capacity for self repair and recovery, and through the often considerable cobenefits they provide, ecosystems can offer notable advantages over traditional engineering approaches in some settings. They can also be combined in "hybrid" engineering designs. We make 10 recommendations to encourage the utilization of existing knowledge and to improve the incorporation of ecosystems into policy, planning and funding for coastal hazard risk reduction.