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Ueda C, Langton M, Chen J, Pandelia ME. The HBx protein from hepatitis B virus coordinates a redox-active Fe-S cluster. J Biol Chem 2022; 298:101698. [PMID: 35148994 PMCID: PMC9010755 DOI: 10.1016/j.jbc.2022.101698] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 02/03/2022] [Accepted: 02/04/2022] [Indexed: 12/17/2022] Open
Abstract
The viral protein HBx is the key regulatory factor of the hepatitis B virus (HBV) and the main etiology for HBV-associated liver diseases, such as cirrhosis and hepatocellular carcinoma. Historically, HBx has defied biochemical and structural characterization, deterring efforts to understand its molecular mechanisms. Here we show that soluble HBx fused to solubility tags copurifies with either a [2Fe-2S] or a [4Fe-4S] cluster, a feature that is shared among five HBV genotypes. We show that the O2-stable [2Fe-2S] cluster form converts to an O2-sensitive [4Fe-4S] state when reacted with chemical reductants, a transformation that is best described by a reductive coupling mechanism reminiscent of Fe-S cluster scaffold proteins. In addition, the Fe-S cluster conversions are partially reversible in successive reduction-oxidation cycles, with cluster loss mainly occurring during (re)oxidation. The considerably negative reduction potential of the [4Fe-4S]2+/1+ couple (-520 mV) suggests that electron transfer may not be likely in the cell. Collectively, our findings identify HBx as an Fe-S protein with striking similarities to Fe-S scaffold proteins both in cluster type and reductive transformation. An Fe-S cluster in HBx offers new insights into its previously unknown molecular properties and sets the stage for deciphering the roles of HBx-associated iron (mis)regulation and reactive oxygen species in the context of liver tumorigenesis.
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Affiliation(s)
- Chie Ueda
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts, USA
| | - Michelle Langton
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts, USA
| | - Jiahua Chen
- Department of Biochemistry, Brandeis University, Waltham, Massachusetts, USA
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2
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Fe-S clusters masquerading as zinc finger proteins. J Inorg Biochem 2022; 230:111756. [DOI: 10.1016/j.jinorgbio.2022.111756] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 02/01/2022] [Accepted: 02/06/2022] [Indexed: 02/06/2023]
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3
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Benavides MA. L-Methionine May Modulate the Assembly of SARS-CoV-2 by Interfering with the Mechanism of RNA Polymerase. Med Hypotheses 2022; 161:110798. [PMID: 35185264 PMCID: PMC8841269 DOI: 10.1016/j.mehy.2022.110798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 01/12/2022] [Accepted: 02/11/2022] [Indexed: 11/18/2022]
Abstract
Coronaviruses have received worldwide attention following several severe acute respiratory syndrome (SARS) epidemics. In 2019, the first case of coronavirus disease (COVID-19) caused by a novel coronavirus (SARS-coronavirus 2 [CoV-2]) was reported. SARS-CoV-2 employs RNA-dependent RNA polymerase (RdRp) for genome replication and gene transcription. Recent studies have identified a sulfur (S) metal-binding site in the zinc center structures of the RdRp complex. This metal-binding site is essential for the proper functioning of the viral helicase. We hypothesize that the use of essential nutrients can permeabilize the cell membranes. The oxidation of the metal-binding site occurs via analogs of the essential S-containing amino acid, l-Methionine. l-Methionine can operate as a carrier, and its binding would cause the potential disassembly of RdRp via the S complex and drive methyl donors via a possible countercurrent exchange mechanism and electrical-chemical gradient leading to SARS-CoV-2 replication failure. Our previously published hypothesis on the control of cancer cell proliferation suggests that the presence of a novel disulfide/methyl- adenosine triphosphate pump as an energy source would allow this process. The S binding site in l-Methionine serves as a potential target cofactor for SARS-CoV RdRp, thus providing a possible avenue for the future development of vaccines and antiviral therapeutic strategies to combat COVID-19.
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4
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Maio N, Lafont BAP, Sil D, Li Y, Bollinger JM, Krebs C, Pierson TC, Linehan WM, Rouault TA. Fe-S cofactors in the SARS-CoV-2 RNA-dependent RNA polymerase are potential antiviral targets. Science 2021; 373:236-241. [PMID: 34083449 PMCID: PMC8892629 DOI: 10.1126/science.abi5224] [Citation(s) in RCA: 62] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 05/28/2021] [Indexed: 01/18/2023]
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causal agent of COVID-19, uses an RNA-dependent RNA polymerase (RdRp) for the replication of its genome and the transcription of its genes. We found that the catalytic subunit of the RdRp, nsp12, ligates two iron-sulfur metal cofactors in sites that were modeled as zinc centers in the available cryo-electron microscopy structures of the RdRp complex. These metal binding sites are essential for replication and for interaction with the viral helicase. Oxidation of the clusters by the stable nitroxide TEMPOL caused their disassembly, potently inhibited the RdRp, and blocked SARS-CoV-2 replication in cell culture. These iron-sulfur clusters thus serve as cofactors for the SARS-CoV-2 RdRp and are targets for therapy of COVID-19.
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Affiliation(s)
- Nunziata Maio
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Bernard A P Lafont
- SARS-CoV-2 Virology Core, Laboratory of Viral Diseases, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Debangsu Sil
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA
| | - Yan Li
- Proteomics Core Facility, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
| | - J Martin Bollinger
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.,Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Carsten Krebs
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.,Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA
| | - Theodore C Pierson
- Laboratory of Viral Diseases, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - W Marston Linehan
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Tracey A Rouault
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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5
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Pritts JD, Oluyadi AA, Huang W, Shimberg GD, Kane MA, Wilks A, Michel SLJ. Understanding RNA Binding by the Nonclassical Zinc Finger Protein CPSF30, a Key Factor in Polyadenylation during Pre-mRNA Processing. Biochemistry 2021; 60:780-790. [PMID: 33615774 DOI: 10.1021/acs.biochem.0c00940] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Cleavage and polyadenylation specificity factor 30 (CPSF30) is a zinc finger protein that regulates pre-mRNA processing. CPSF30 contains five CCCH domains and one CCHC domain and recognizes two conserved 3' pre-mRNA sequences: an AU hexamer and a U-rich motif. AU hexamer motifs are common in pre-mRNAs and are typically defined as AAUAAA. Variations within the AAUAAA hexamer occur in certain pre-mRNAs and can affect polyadenylation efficiency or be linked to diseases. The effects of disease-related variations on CPSF30/pre-mRNA binding were determined using a construct of CPSF30 that contains just the five CCCH domains (CPSF30-5F). Bioinformatics was utilized to identify the variability within the AU hexamer sequence in pre-mRNAs. The effects of this sequence variability on CPSF30-5F/RNA binding affinities were measured. Bases at positions 1, 2, 4, and 5 within the AU hexamer were found to be important for RNA binding. Bioinformatics revealed that the three bases flanking the AU hexamer at the 5' and 3' ends are twice as likely to be adenine or uracil as guanine and cytosine. The presence of A and U residues in these flanking regions was determined to promote higher-affinity CPSF30-5F/RNA binding than G and C residues. The addition of the zinc knuckle domain to CPSF30-5F (CPSF30-FL) restored binding to AU hexamer variants. This restoration of binding is connected to the presence of a U-rich sequence within the pre-mRNA to which the zinc knuckle binds. A mechanism of differential RNA binding by CPSF30, modulated by accessibility of the two RNA binding sites, is proposed.
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Affiliation(s)
- Jordan D Pritts
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Abdulafeez A Oluyadi
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Weiliang Huang
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Geoffrey D Shimberg
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Maureen A Kane
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Angela Wilks
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Sarah L J Michel
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
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6
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Silva RMB, Grodick MA, Barton JK. UvrC Coordinates an O 2-Sensitive [4Fe4S] Cofactor. J Am Chem Soc 2020; 142:10964-10977. [PMID: 32470300 DOI: 10.1021/jacs.0c01671] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent advances have led to numerous landmark discoveries of [4Fe4S] clusters coordinated by essential enzymes in repair, replication, and transcription across all domains of life. The cofactor has notably been challenging to observe for many nucleic acid processing enzymes due to several factors, including a weak bioinformatic signature of the coordinating cysteines and lability of the metal cofactor. To overcome these challenges, we have used sequence alignments, an anaerobic purification method, iron quantification, and UV-visible and electron paramagnetic resonance spectroscopies to investigate UvrC, the dual-incision endonuclease in the bacterial nucleotide excision repair (NER) pathway. The characteristics of UvrC are consistent with [4Fe4S] coordination with 60-70% cofactor incorporation, and additionally, we show that, bound to UvrC, the [4Fe4S] cofactor is susceptible to oxidative degradation with aggregation of apo species. Importantly, in its holo form with the cofactor bound, UvrC forms high affinity complexes with duplexed DNA substrates; the apparent dissociation constants to well-matched and damaged duplex substrates are 100 ± 20 nM and 80 ± 30 nM, respectively. This high affinity DNA binding contrasts reports made for isolated protein lacking the cofactor. Moreover, using DNA electrochemistry, we find that the cluster coordinated by UvrC is redox-active and participates in DNA-mediated charge transport chemistry with a DNA-bound midpoint potential of 90 mV vs NHE. This work highlights that the [4Fe4S] center is critical to UvrC.
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Affiliation(s)
- Rebekah M B Silva
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Michael A Grodick
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jacqueline K Barton
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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7
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Maio N, Jain A, Rouault TA. Mammalian iron-sulfur cluster biogenesis: Recent insights into the roles of frataxin, acyl carrier protein and ATPase-mediated transfer to recipient proteins. Curr Opin Chem Biol 2020; 55:34-44. [PMID: 31918395 PMCID: PMC7237328 DOI: 10.1016/j.cbpa.2019.11.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 11/20/2019] [Accepted: 11/30/2019] [Indexed: 12/31/2022]
Abstract
The recently solved crystal structures of the human cysteine desulfurase NFS1, in complex with the LYR protein ISD11, the acyl carrier protein ACP, and the main scaffold ISCU, have shed light on the molecular interactions that govern initial cluster assembly on ISCU. Here, we aim to highlight recent insights into iron-sulfur (Fe-S) cluster (ISC) biogenesis in mammalian cells that have arisen from the crystal structures of the core ISC assembly complex. We will also discuss how ISCs are delivered to recipient proteins and the challenges that remain in dissecting the pathways that deliver clusters to numerous Fe-S recipient proteins in both the mitochondrial matrix and cytosolic compartments of mammalian cells.
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Affiliation(s)
- Nunziata Maio
- Molecular Medicine Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Anshika Jain
- Molecular Medicine Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Tracey A Rouault
- Molecular Medicine Branch, Eunice Kennedy Shriver National Institute of Child Health and Human Development, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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8
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Pritts JD, Hursey MS, Michalek JL, Batelu S, Stemmler TL, Michel SLJ. Unraveling the RNA Binding Properties of the Iron-Sulfur Zinc Finger Protein CPSF30. Biochemistry 2020; 59:970-982. [PMID: 32027124 DOI: 10.1021/acs.biochem.9b01065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cleavage and polyadenylation specificity factor 30 (CPSF30) is a "zinc finger" protein that plays a crucial role in the transition of pre-mRNA to RNA. CPSF30 contains five conserved CCCH domains and a CCHC "zinc knuckle" domain. CPSF30 activity is critical for pre-mRNA processing. A truncated form of the protein, in which only the CCCH domains are present, has been shown to specifically bind AU-rich pre-mRNA targets; however, the RNA binding and recognition properties of full-length CPSF30 are not known. Herein, we report the isolation and biochemical characterization of full-length CPSF30. We report that CPSF30 contains one 2Fe-2S cluster in addition to five zinc ions, as measured by inductively coupled plasma mass spectrometry, ultraviolet-visible spectroscopy, and X-ray absorption spectroscopy. Utilizing fluorescence anisotropy RNA binding assays, we show that full-length CPSF30 has high binding affinity for two types of pre-mRNA targets, AAUAAA and polyU, both of which are conserved sequence motifs present in the majority of pre-mRNAs. Binding to the AAUAAA motif requires that the five CCCH domains of CPSF30 be present, whereas binding to polyU sequences requires the entire, full-length CPSF30. These findings implicate the CCHC "zinc knuckle" present in the full-length protein as being critical for mediating polyU binding. We also report that truncated forms of the protein, containing either just two CCCH domains (ZF2 and ZF3) or the CCHC "zinc knuckle" domain, do not exhibit any RNA binding, indicating that CPSF30/RNA binding requires several ZF (and/or Fe-S cluster) domains working in concert to mediate RNA recognition.
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Affiliation(s)
- Jordan D Pritts
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Matthew S Hursey
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Jamie L Michalek
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
| | - Sharon Batelu
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201, United States
| | - Timothy L Stemmler
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, Michigan 48201, United States
| | - Sarah L J Michel
- Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland, Baltimore, Maryland 21201-1180, United States
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9
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Şişli HB, Hayal TB, Seçkin S, Şenkal S, Kıratlı B, Şahin F, Doğan A. Gene Editing in Human Pluripotent Stem Cells: Recent Advances for Clinical Therapies. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1237:17-28. [PMID: 31728915 DOI: 10.1007/5584_2019_439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The identification of human embryonic stem cells and reprogramming technology to obtain induced pluripotent stem cells from adult somatic cells have provided unique opportunity to create human disease models, gene editing strategies and cell therapy options.Development of pluripotent stem cells from somatic cells and genomic manipulation tools enabled to use site specific nucleases in the cell therapy research. Identification of efficient gene manipulation, safe differentiation and use will provide a novel strategy to treat many diseases in the near future. Current available registered clinical trials clearly indicate the need for pluripotent stem cell and gene therapy treatment options. Although gene editing based pluripotent stem cell research is a popular field for research worldwide, improvement of clinical approaches for treatment still remains to be investigated. In this review, we summarized the current situation of gene editing based pluripotent cell therapy developments and applications in clinics.
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Affiliation(s)
- Hatice Burcu Şişli
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, Istanbul, Turkey
| | - Taha Bartu Hayal
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, Istanbul, Turkey
| | - Selin Seçkin
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, Istanbul, Turkey
| | - Selinay Şenkal
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, Istanbul, Turkey
| | - Binnur Kıratlı
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, Istanbul, Turkey
| | - Fikrettin Şahin
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, Istanbul, Turkey
| | - Ayşegül Doğan
- Department of Genetics and Bioengineering, Faculty of Engineering, Yeditepe University, Istanbul, Turkey.
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Gaur K, Vázquez-Salgado A, Duran-Camacho G, Dominguez-Martinez I, Benjamín-Rivera J, Fernández-Vega L, Carmona Sarabia L, Cruz García A, Pérez-Deliz F, Méndez Román J, Vega-Cartagena M, Loza-Rosas S, Rodriguez Acevedo X, Tinoco A. Iron and Copper Intracellular Chelation as an Anticancer Drug Strategy. INORGANICS 2018. [DOI: https://doi.org/10.3390/inorganics6040126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A very promising direction in the development of anticancer drugs is inhibiting the molecular pathways that keep cancer cells alive and able to metastasize. Copper and iron are two essential metals that play significant roles in the rapid proliferation of cancer cells and several chelators have been studied to suppress the bioavailability of these metals in the cells. This review discusses the major contributions that Cu and Fe play in the progression and spreading of cancer and evaluates select Cu and Fe chelators that demonstrate great promise as anticancer drugs. Efforts to improve the cellular delivery, efficacy, and tumor responsiveness of these chelators are also presented including a transmetallation strategy for dual targeting of Cu and Fe. To elucidate the effectiveness and specificity of Cu and Fe chelators for treating cancer, analytical tools are described for measuring Cu and Fe levels and for tracking the metals in cells, tissue, and the body.
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Gaur K, Vázquez-Salgado AM, Duran-Camacho G, Dominguez-Martinez I, Benjamín-Rivera JA, Fernández-Vega L, Sarabia LC, García AC, Pérez-Deliz F, Méndez Román JA, Vega-Cartagena M, Loza-Rosas SA, Acevedo XR, Tinoco AD. Iron and Copper Intracellular Chelation as an Anticancer Drug Strategy. INORGANICS 2018; 6:126. [PMID: 33912613 PMCID: PMC8078164 DOI: 10.3390/inorganics6040126] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
A very promising direction in the development of anticancer drugs is inhibiting the molecular pathways that keep cancer cells alive and able to metastasize. Copper and iron are two essential metals that play significant roles in the rapid proliferation of cancer cells and several chelators have been studied to suppress the bioavailability of these metals in the cells. This review discusses the major contributions that Cu and Fe play in the progression and spreading of cancer and evaluates select Cu and Fe chelators that demonstrate great promise as anticancer drugs. Efforts to improve the cellular delivery, efficacy, and tumor responsiveness of these chelators are also presented including a transmetallation strategy for dual targeting of Cu and Fe. To elucidate the effectiveness and specificity of Cu and Fe chelators for treating cancer, analytical tools are described for measuring Cu and Fe levels and for tracking the metals in cells, tissue, and the body.
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Affiliation(s)
- Kavita Gaur
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | | | - Geraldo Duran-Camacho
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | | | - Josué A Benjamín-Rivera
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | - Lauren Fernández-Vega
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | - Lesly Carmona Sarabia
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | - Angelys Cruz García
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | - Felipe Pérez-Deliz
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | - José A Méndez Román
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | - Melissa Vega-Cartagena
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | - Sergio A Loza-Rosas
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
| | | | - Arthur D Tinoco
- Department of Chemistry, University of Puerto Rico, Río Piedras Campus, Río Piedras, PR 00931, USA
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