Chen H.,Cornell University |
Ahsan S.S.,Cornell University |
Santiago-Berrios M.B.,University of Puerto Rico at Cayey |
Abruna H.D.,Cornell University |
Webb W.W.,Cornell University
Journal of the American Chemical Society | Year: 2010
Quenching of fluorophores by the same proteins that they covalently label is a phenomenon that is neither well-known nor well-characterized. It is often assumed that fluorophores are unperturbed by their target proteins. However, it has been observed that attached fluorophores can be quenched by contact with amino acids within the same protein, and this property has been exploited to report on changing conformational states or intramolecular dynamics of proteins. We show in this communication that fluorescence of Alexa dyes is, in fact, quenched by interactions with Trp, Tyr, Met, and His residues through a combination of static and dynamic quenching mechanisms. In light of this finding, the potential effect of intramolecular quenching should be considered in the interpretation of data that involves quantitative measurements of fluorescence intensity in proteins.
Munoz J.L.,Rutgers University |
Rodriguez-Cruz V.,University of Puerto Rico at Cayey |
Greco S.J.,Rutgers University |
Nagula V.,Rutgers University |
And 2 more authors.
Molecular Cancer Therapeutics | Year: 2014
Glioblastoma multiforme (GBM) commonly resists the frontline chemotherapy treatment temozolomide. The multidrug resistance gene (MDR1) and its protein, P-glycoprotein (P-gp), are associated with chemoresistance. This study investigated the mechanisms underlying MDR1-mediated resistance by GBM to temozolomide. P-gp trafficking was studied by flow cytometry and Western blot analysis. MDR1 expression was analyzed by real-time PCR and reporter gene assays. AP-1 interaction with MDR1 was studied by chromatin immunoprecipitation assay. EGF production was analyzed by ELISA, EGFR signaling was determined by Western blot analysis, and in vivo response to erlotinib and/or temozolomide was studied in nude mice. During the early phase of temozolomide treatment, intracellular P-gp was trafficked to the cell membrane, followed by conformational change into active P-gp. At the later phase, gene transcription of MDR1 was induced by temozolomide-mediated production of EGF. EGF activated ERK1/2-JNK-AP-1 cofactors (c-jun and c-fos). An inhibitor of EGFR kinase (erlotinib) given to nude mice with GBM prevented temozolomide-induced resistance. The results identified an essential role for activated EGFR in the resistance of GBM to temozolomide. Temozolomide resistance occurred through a biphasic response; first, by a conformational change in P-gp into the active form and, second, by releasing EGF, which caused autocrine stimulation of GBM cells to induce MDR1. Pharmacologic inhibition of EGFR kinase blunted the ability of GBM cells to resist temozolomide. These findings mayexplain reports on the common occurrence of mutant EGFR (EGFRvIII) and EGFR expansion in the resistance of GBM cells. ©2014 AACR.
Annamalai N.,University of Puerto Rico at Cayey |
Rajeswari M.V.,Annamalai University |
Elayaraja S.,Annamalai University |
Balasubramanian T.,Annamalai University
Carbohydrate Polymers | Year: 2013
An extracellular thermostable, haloalkaline cellulase by bioconversion of lignocellulosic wastes from Bacillus halodurans CAS 1 was purified to homogeneity with recovery of 12.54% and purity fold 7.96 with the molecular weight of 44 kDa. The optimum temperature, pH and NaCl for enzyme activity was determined as 60 °C, 9.0 and 30% and it retained 80% of activity even at 80 °C, 12 and 35% respectively. The activity was greatly inhibited by EDTA, indicating that it was a metalloenzyme and significant inhibition by PMSF revealed that serine residue was essential for catalytic activity. The purified cellulase hydrolyzed CMC, cellobiose and xylan, but not avicel, cellulose and PNPG. Furthermore, the cellulase was highly stable in the presence of detergents and organic solvents such as acetone, n-hexane and acetonitrile. Thus, the purified cellulase from B. halodurans utilizing lignocellulosic biomass could be greatly useful to develop industrial processes.
Mitchell K.F.,University of Wisconsin - Madison |
Taff H.T.,University of Wisconsin - Madison |
Cuevas M.A.,University of Puerto Rico at Cayey |
Reinicke E.L.,University of Wisconsin - Madison |
And 2 more authors.
Antimicrobial Agents and Chemotherapy | Year: 2013
Candida biofilm infections pose an increasing threat in the health care setting due to the drug resistance associated with this lifestyle. Several mechanisms underlie the resistance phenomenon. In Candida albicans, one mechanism involves drug impedance by the biofilm matrix linked to β-1,3 glucan. Here, we show this is important for other Candida spp. We identified β-1,3 glucan in the matrix, found that the matrix sequesters antifungal drug, and enhanced antifungal susceptibility with matrix β-1,3 glucan hydrolysis. Copyright © 2013, American Society for Microbiology. All Rights Reserved.
Arce-Nazario J.A.,University of Puerto Rico at Cayey
Journal of Sustainable Forestry | Year: 2011
Agriculture is commonly considered a human disturbance which homogenizes the landscape, reducing the diversity of ecosystem services. Nevertheless, small-scale farming in the Amazon has had a tradition of diversifying the landscape and taking advantage of multiple habitats. Previous studies have described this process at a broad and general scale. In this study, I consider spatial distributionsin detail to analyze the intricate relationships between space and management. Forest inventories, remote sensing analysis, and1-dm scale topographic surveys of a 22-ha family landholding were performed and mapped. Interviews and participant observation were also used to learn about the farmers' management decisions in their landholding. The results show that the biophysical heterogeneity, the diversification of productive spaces, and the conservation of extensive interconnected forest patches have enabled farmers to explore management strategies incorporating the Amazon's fluvial dynamics. These heterogeneous spaces have provided the farmers with ecosystem services that ultimately feed back into the household economy and allow them to respond to shifting markets and shifting river dynamics. Hence, these fine-scale patterns deserve further study as options to be promoted in future conservation and agroforestry policies in the Amazon. © Taylor & Francis Group, LLC.
Arce-Nazario J.A.,University of Puerto Rico at Cayey
Journal of Land Use Science | Year: 2016
For land-use science to engage the general public it must successfully translate its concepts and conclusions and make them public outside of traditional scientific venues. Here we explore science-art exhibits, which blend artistic presentations with specific scientific data or themes, as a possible effective way of communicating scientific information and disrupting misconceptions. We describe the process of producing a science-art exhibit on remote sensing and Puerto Rican landscape history from 1937 to the present, sited at a rural Puerto Rican community museum, and examine the visitor experience and educational outcomes of the museum exhibit through analysis of survey data. The exhibit project engaged undergraduate students from a variety of academic backgrounds, introduced land-use science concepts to the public in an engaging format, and was effective at reshaping visitors’ misconceptions of Puerto Rico’s landscape change history. © 2016, Taylor & Francis. All rights reserved.
Herrera-Valdez M.A.,University of Arizona |
Herrera-Valdez M.A.,University of Puerto Rico at Cayey
PLoS ONE | Year: 2012
Electrical signaling allows communication within and between different tissues and is necessary for the survival of multicellular organisms. The ionic transport that underlies transmembrane currents in cells is mediated by transporters and channels. Fast ionic transport through channels is typically modeled with a conductance-based formulation that describes current in terms of electrical drift without diffusion. In contrast, currents written in terms of drift and diffusion are not as widely used in the literature in spite of being more realistic and capable of displaying experimentally observable phenomena that conductance-based models cannot reproduce (e.g. rectification). The two formulations are mathematically related: conductance-based currents are linear approximations of drift-diffusion currents. However, conductance-based models of membrane potential are not first-order approximations of drift-diffusion models. Bifurcation analysis and numerical simulations show that the two approaches predict qualitatively and quantitatively different behaviors in the dynamics of membrane potential. For instance, two neuronal membrane models with identical populations of ion channels, one written with conductance-based currents, the other with drift-diffusion currents, undergo transitions into and out of repetitive oscillations through different mechanisms and for different levels of stimulation. These differences in excitability are observed in response to excitatory synaptic input, and across different levels of ion channel expression. In general, the electrophysiological profiles of membranes modeled with drift-diffusion and conductance-based models having identical ion channel populations are different, potentially causing the input-output and computational properties of networks constructed with these models to be different as well. The drift-diffusion formulation is thus proposed as a theoretical improvement over conductance-based models that may lead to more accurate predictions and interpretations of experimental data at the single cell and network levels. © 2012 Marco Arieli Herrera-Valdez.
Uriarte M.,Columbia University |
Yackulic C.B.,Columbia University |
Lim Y.,Columbia University |
Arce-Nazario J.A.,University of Puerto Rico at Cayey
Landscape Ecology | Year: 2011
There is a pressing need to understand the consequences of human activities, such as land transformations, on watershed ecosystem services. This is a challenging task because different indicators of water quality and yield are expected to vary in their responsiveness to large versus local-scale heterogeneity in land use and land cover (LUC). Here we rely on water quality data collected between 1977 and 2000 from dozens of gauge stations in Puerto Rico together with precipitation data and land cover maps to (1) quantify impacts of spatial heterogeneity in LUC on several water quality indicators; (2) determine the spatial scale at which this heterogeneity influences water quality; and (3) examine how antecedent precipitation modulates these impacts. Our models explained 30-58% of observed variance in water quality metrics. Temporal variation in antecedent precipitation and changes in LUC between measurements periods rather than spatial variation in LUC accounted for the majority of variation in water quality. Urbanization and pasture development generally degraded water quality while agriculture and secondary forest re-growth had mixed impacts. The spatial scale over which LUC influenced water quality differed across indicators. Turbidity and dissolved oxygen (DO) responded to LUC in large-scale watersheds, in-stream nitrogen concentrations to LUC in riparian buffers of large watersheds, and fecal matter content and in-stream phosphorus concentration to LUC at the sub-watershed scale. Stream discharge modulated impacts of LUC on water quality for most of the metrics. Our findings highlight the importance of considering multiple spatial scales for understanding the impacts of human activities on watershed ecosystem services. © 2011 Springer Science+Business Media B.V.
Santana J.A.,University of Puerto Rico at Cayey
Atomic Data and Nuclear Data Tables | Year: 2016
The relativistic Multi-Reference Møller-Plesset (MR-MP) many-body perturbation theory was applied to calculate the energies of all excited states within the 3s3p, 3p2, 3s3d, 3p3d and 3d2 configurations for every ion of the Mg isoelectronic sequence (Z=12-100). The results are compared with previous calculations and available experimental data. The MR-MP excitation energies agree with experiment typically within 100 ppm over a wide range of Z, particularly for mid- and high-range Z. Experimental data for highly charged ions in this isoelectronic sequence are limited and the complete and accurate dataset presented here is expected to ease the identification process upon measurements. © 2016 Published by Elsevier Inc.
Agency: NSF | Branch: Continuing grant | Program: | Phase: GEOGRAPHY AND SPATIAL SCIENCES | Award Amount: 493.66K | Year: 2012
Given the likelihood that climate change will result in changes to the hydrologic cycle, it is important to understand how extreme precipitation events may affect water systems. This project will analyze how biophysical and socioeconomic elements of the landscape affect water quality and the adaptability of water systems to extreme precipitation events, to understand water resource sustainability under stress. Climate change scenarios suggest more frequent extreme precipitation events and extended droughts, increasing the effect of contaminants on streams and underground aquifers. These events may also affect the resilience of social institutions and built structures that are necessary for water quality management and water distribution. This research will specifically address two central questions about changes in precipitation: first, how the spatial distribution and composition of land cover and land use in a watershed affects water quality when a region is exposed to extreme precipitation events, and second, which aspects of water governance promote sustainable, reliable sources of clean water in the region. The research will be carried out in the La Plata Watershed in Puerto Rico, which has been exposed to large precipitation extremes from multiple hurricanes and displays a diversity of water management systems. By reconstructing the history of land cover change, stream water quality, water governance, and extreme precipitation events in the La Plata Watershed, this project will produce models that explain the primary factors that affect water quality and sustainability. The field site is close to the University of Puerto Rico in Cayey, which will allow the field research methods and the knowledge obtained from this project to be integrated into an undergraduate science curriculum. Implementing and assessing new student-centered education course components based on this field research will lead to new strategies to integrate research into education and bolster student engagement in science.
The project will give new insights into how changes in land cover, precipitation events and water management affect water quality and sustainability. Understanding these processes is needed to address the complex human-environmental dynamics that are characteristic of climate change problems. By demonstrating which social and environmental factors enhance water quality and sustainable access to potable water, these results may impact water policies and help define better water resource management strategies that can adapt to climate change. Planned community interactions will create awareness about the collection of scientific data, local water quality issues, and the impact of geography on clean, sustainable water. Finally, the project will enhance science education by integrating field research experience and training in spatial thinking into undergraduate courses at a minority serving institution.