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Jurado Z, Murray RM. Impact of Chemical Dynamics of Commercial PURE Systems on Malachite Green Aptamer Fluorescence. ACS Synth Biol 2024. [PMID: 39287516 DOI: 10.1021/acssynbio.4c00211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2024]
Abstract
The malachite green aptamer (MGapt) is known for its utility in RNA measurement in vivo and in lysate-based cell-free protein systems. However, MGapt fluorescence dynamics do not accurately reflect RNA concentration. Our study finds that MGapt fluorescence is unstable in commercial PURE systems. We discovered that the chemical composition of the cell-free reaction strongly influences MGapt fluorescence, which leads to inaccurate RNA calculations. Specific to the commercial system, we posit that MGapt fluorescence is significantly affected by the system's chemical properties, governed notably by the presence of dithiothreitol (DTT). We propose a model that, on average, accurately predicts MGapt measurement within a 10% margin, leveraging DTT concentration as a critical factor. This model sheds light on the complex dynamics of MGapt in cell-free systems and underscores the importance of considering environmental factors in RNA measurements using aptamers.
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Affiliation(s)
- Zoila Jurado
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91106, United States
| | - Richard M Murray
- Division of Engineering and Applied Science, California Institute of Technology, Pasadena, California 91106, United States
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2
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Cowan JA. Understanding the Thermodynamics of Magnesium Binding to RNA Structural Motifs. Life (Basel) 2024; 14:765. [PMID: 38929748 PMCID: PMC11205036 DOI: 10.3390/life14060765] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 06/05/2024] [Accepted: 06/12/2024] [Indexed: 06/28/2024] Open
Abstract
Divalent magnesium ions (Mg2+) serve a vital role in defining the structural and catalytic chemistry of a wide array of RNA molecules. The body of structural information on RNA motifs continues to expand and, in turn, the functional importance of Mg2+ is revealed. A combination of prior work on the structural characterization of magnesium binding ligands with inner- and outer-sphere coordination modes, with recorded experimental binding energies for inner- and outer-sphere contacts, demonstrates the relative affinity and thermodynamic hierarchy for these sites. In turn, these can be correlated with cellular concentrations of free available magnesium ions, allowing the prioritization of populating important functional sites and a correlation with physiological function. This paper summarizes some of the key results of that analysis and provides predictive rules for the affinity and role of newly identified Mg binding sites on complex RNA structures. The influence of crystal packing on magnesium binding to RNA motifs, relative to their solution form, is addressed and caveats made.
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Affiliation(s)
- J A Cowan
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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3
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Saha R, Kao WL, Malady B, Heng X, Chen IA. Effect of montmorillonite K10 clay on RNA structure and function. Biophys J 2024; 123:451-463. [PMID: 37924206 PMCID: PMC10912936 DOI: 10.1016/j.bpj.2023.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 09/29/2023] [Accepted: 11/01/2023] [Indexed: 11/06/2023] Open
Abstract
One of the earliest living systems was likely based on RNA ("the RNA world"). Mineral surfaces have been postulated to be an important environment for the prebiotic chemistry of RNA. In addition to adsorbing RNA and thus potentially reducing the chance of parasitic takeover through limited diffusion, minerals have been shown to promote a range of processes related to the emergence of life, including RNA polymerization, peptide bond formation, and self-assembly of vesicles. In addition, self-cleaving ribozymes have been shown to retain activity when adsorbed to the clay mineral montmorillonite. However, simulation studies suggest that adsorption to minerals is likely to interfere with RNA folding and, thus, function. To further evaluate the plausibility of a mineral-adsorbed RNA world, here we studied the effect of the synthetic clay montmorillonite K10 on the malachite green RNA aptamer, including binding of the clay to malachite green and RNA, as well as on the formation of secondary structures in model RNA and DNA oligonucleotides. We evaluated the fluorescence of the aptamer complex, adsorption to the mineral, melting curves, Förster resonance energy transfer interactions, and 1H-NMR signals to study the folding and functionality of these nucleic acids. Our results indicate that while some base pairings are unperturbed, the overall folding and binding of the malachite green aptamer are substantially disrupted by montmorillonite. These findings suggest that minerals would constrain the structures, and possibly the functions, available to an adsorbed RNA world.
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Affiliation(s)
- Ranajay Saha
- Department of Chemical and Biomolecular Engineering, Department of Chemistry and Biochemistry, University of California, Los Angeles, California; Department of Chemistry and Biochemistry, University of California, Santa Barbara, California
| | - Wei-Ling Kao
- Department of Biochemistry, University of Missouri, Columbia, Missouri
| | - Brandon Malady
- Department of Chemistry and Biochemistry, University of California, Santa Barbara, California
| | - Xiao Heng
- Department of Biochemistry, University of Missouri, Columbia, Missouri
| | - Irene A Chen
- Department of Chemical and Biomolecular Engineering, Department of Chemistry and Biochemistry, University of California, Los Angeles, California; Department of Chemistry and Biochemistry, University of California, Santa Barbara, California.
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4
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Chen K, Zhu L, Du Z, Lan X, Huang K, Zhang W, Xu W. Docking-aided rational tailoring of a fluorescence- and affinity-enhancing aptamer for a label-free ratiometric malachite green point-of-care aptasensor. JOURNAL OF HAZARDOUS MATERIALS 2023; 447:130798. [PMID: 36669418 DOI: 10.1016/j.jhazmat.2023.130798] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 01/12/2023] [Accepted: 01/13/2023] [Indexed: 06/17/2023]
Abstract
Although nucleic acid aptasensors are increasingly applied in the detection of environmentally hazardous biomolecules, several formidable challenges remain with this technique because of their vulnerability, high cost and suboptimal sensitivity. Here, a docking-aided rational tailoring (DART) strategy was established at three levels and in two dimensions for the refinement of malachite green (MG) DNA aptamers. Guided by in silico molecular docking, coarse and fine tailoring were conducted at three levels each, to significantly enhance fluorescence activation intensity and binding affinity in two dimensions. Empowered by the results of the rational tailoring, a mechanistic view of the MG DNA aptamer-target interaction was thoroughly analyzed via four types of interactions. To meet the demand for point-of-care testing (POCT), a label-free and ratiometric fluorescent aptasensor was developed leveraging the tailored MG aptamer, based on the binding site competition-equilibrium effect via the introduction of a reference dye. This sensitive, specific, low-cost and rapid aptasensor subsequently demonstrated outstanding detection performance, achieving an ideal signal response range of 5 nmol·L-1 - 6 μmol·L-1 and a low limit of detection (LOD) of 1.49 nmol·L-1. The DART strategy and systematic exploration of the MG DNA luminescent aptamers herein will provide a valuable reference in the field of aptamer tailoring, biosensing and bioimaging. The proposed label-free ratiometric aptasensor also provides a highly generalizable strategy for hazardous biomolecular detection.
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Affiliation(s)
- Keren Chen
- Food Laboratory of Zhongyuan, Key Laboratory of Precision Nutrition and Food Quality, Department of Nutrition and Health, China Agricultural University, Beijing 100193, China; Key Laboratory of Safety Assessment of Genetically Modified Organism (Food Safety), College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Longjiao Zhu
- Food Laboratory of Zhongyuan, Key Laboratory of Precision Nutrition and Food Quality, Department of Nutrition and Health, China Agricultural University, Beijing 100193, China
| | - Zaihui Du
- Food Laboratory of Zhongyuan, Key Laboratory of Precision Nutrition and Food Quality, Department of Nutrition and Health, China Agricultural University, Beijing 100193, China; Key Laboratory of Safety Assessment of Genetically Modified Organism (Food Safety), College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Xinyue Lan
- Food Laboratory of Zhongyuan, Key Laboratory of Precision Nutrition and Food Quality, Department of Nutrition and Health, China Agricultural University, Beijing 100193, China; Key Laboratory of Safety Assessment of Genetically Modified Organism (Food Safety), College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Kunlun Huang
- Key Laboratory of Safety Assessment of Genetically Modified Organism (Food Safety), College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China
| | - Wenqiang Zhang
- Department of Mechanical Design and Manufacturing, College of Engineering, China Agricultural University, Beijing 100083, China
| | - Wentao Xu
- Food Laboratory of Zhongyuan, Key Laboratory of Precision Nutrition and Food Quality, Department of Nutrition and Health, China Agricultural University, Beijing 100193, China; Key Laboratory of Safety Assessment of Genetically Modified Organism (Food Safety), College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China.
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5
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Michel M, Homan EJ, Wiita E, Pedersen K, Almlöf I, Gustavsson AL, Lundbäck T, Helleday T, Warpman Berglund U. In silico Druggability Assessment of the NUDIX Hydrolase Protein Family as a Workflow for Target Prioritization. Front Chem 2020; 8:443. [PMID: 32548091 PMCID: PMC7274155 DOI: 10.3389/fchem.2020.00443] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 04/28/2020] [Indexed: 01/13/2023] Open
Abstract
Computational chemistry has now been widely accepted as a useful tool for shortening lead times in early drug discovery. When selecting new potential drug targets, it is important to assess the likelihood of finding suitable starting points for lead generation before pursuing costly high-throughput screening campaigns. By exploiting available high-resolution crystal structures, an in silico druggability assessment can facilitate the decision of whether, and in cases where several protein family members exist, which of these to pursue experimentally. Many of the algorithms and software suites commonly applied for in silico druggability assessment are complex, technically challenging and not always user-friendly. Here we applied the intuitive open access servers of DoGSite, FTMap and CryptoSite to comprehensively predict ligand binding pockets, druggability scores and conformationally active regions of the NUDIX protein family. In parallel we analyzed potential ligand binding sites, their druggability and pocket parameter using Schrödinger's SiteMap. Then an in silico docking cascade of a subset of the ZINC FragNow library using the Glide docking program was performed to assess identified pockets for large-scale small-molecule binding. Subsequently, this initial dual ranking of druggable sites within the NUDIX protein family was benchmarked against experimental hit rates obtained both in-house and by others from traditional biochemical and fragment screening campaigns. The observed correlation suggests that the presented user-friendly workflow of a dual parallel in silico druggability assessment is applicable as a standalone method for decision on target prioritization and exclusion in future screening campaigns.
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Affiliation(s)
- Maurice Michel
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Evert J Homan
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Elisée Wiita
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Kia Pedersen
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Ingrid Almlöf
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Anna-Lena Gustavsson
- Chemical Biology Consortium Sweden (CBCS), Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Thomas Lundbäck
- Chemical Biology Consortium Sweden (CBCS), Science for Life Laboratory, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.,Mechanistic Biology and Profiling, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Thomas Helleday
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden.,Department of Oncology and Metabolism, Sheffield Cancer Centre, University of Sheffield, Sheffield, United Kingdom
| | - Ulrika Warpman Berglund
- Science for Life Laboratory, Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
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6
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Cai S, Yan J, Xiong H, Liu Y, Peng D, Liu Z. Investigations on the interface of nucleic acid aptamers and binding targets. Analyst 2019; 143:5317-5338. [PMID: 30357118 DOI: 10.1039/c8an01467a] [Citation(s) in RCA: 161] [Impact Index Per Article: 32.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nucleic acid aptamers are single-stranded DNA or RNA of 20-100 nucleotides in length that have attracted substantial scientific interest due to their ability to specifically bind to target molecules via the formation of three-dimensional structures. Compared to traditional protein antibodies, aptamers have several advantages, such as their small size, high binding affinity, specificity, flexible structure, being chemical synthesizable and modifiable, good biocompatibility, high stability and low immunogenicity, which all contribute to their widely applications in the biomedical field. To date, much progress has been made in the study and applications of aptamers, however, detailed information on how aptamers bind to their targets is still scarce. Over the past few decades, many methods have been introduced to investigate the aptamer-target binding process, such as measuring the main kinetic or thermodynamic parameters, detecting the structural changes of the binding complexes, etc. Apart from traditional physicochemical methods, various types of molecular docking programs have been applied to simulate the aptamer-target interactions, while these simulations also have limitations. To facilitate the further research on the interactions, herein, we provide a brief review to illustrate the recent advances in the study of aptamer-target interactions. We summarize the binding targets of aptamers, such as small molecules, macromolecules, and even cells. Their binding constants (KD) are also summarized. Methods to probe the aptamer-target binding process, such as surface plasmon resonance (SPR), circular dichroism spectroscopy (CD), isothermal titration calorimetry (ITC), footprinting assay, truncation and mutation assay, nuclear magnetic resonance spectroscopy (NMR), X-ray crystallography and molecular docking simulation are indicated. The binding forces mediating the aptamer-target interactions, such as hydrogen bonding, electrostatic interaction, the hydrophobic effect, π-π stacking and van der Waals forces are summarized. The challenges and future perspectives are also discussed.
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Affiliation(s)
- Shundong Cai
- Department of Pharmaceutics, Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, 410013, PR China.
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Zhang Z, Oni O, Liu J. New insights into a classic aptamer: binding sites, cooperativity and more sensitive adenosine detection. Nucleic Acids Res 2017; 45:7593-7601. [PMID: 28591844 PMCID: PMC5737652 DOI: 10.1093/nar/gkx517] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2017] [Accepted: 06/01/2017] [Indexed: 11/27/2022] Open
Abstract
The DNA aptamer for adenosine (also for AMP and ATP) is a highly conserved sequence that has recurred in a few selections. It it a widely used model aptamer for biosensor development, and its nuclear magnetic resonance structure shows that each aptamer binds two AMP molecules. In this work, each binding site was individually removed by rational sequence design, while the remaining site still retained a similar binding affinity and specificity as confirmed by isothermal titration calorimetry. The thermodynamic parameters of binding are presented, and its biochemical implications are discussed. The number of binding sites can also be increased, and up to four sites are introduced in a single DNA sequence. Finally, the different sequences are made into fluorescent biosensors based on the structure-switching signaling aptamer design. The one-site aptamer has 3.8-fold higher sensitivity at lower adenosine concentration with a limit of detection of 9.1 μM adenosine, but weaker fluorescence signal at higher adenosine concentrations, consistent with a moderate cooperativity in the original aptamer. This work has offered insights into a classic aptamer for the relationship between the number of binding sites and sensitivity, and a shorter aptamer for improved biosensor design.
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Affiliation(s)
- Zijie Zhang
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Olatunji Oni
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Juewen Liu
- Department of Chemistry, Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
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8
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Zhou Y, Chi H, Wu Y, Marks RS, Steele TWJ. Organic additives stabilize RNA aptamer binding of malachite green. Talanta 2016; 160:172-182. [PMID: 27591602 DOI: 10.1016/j.talanta.2016.06.067] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 06/29/2016] [Accepted: 06/30/2016] [Indexed: 11/27/2022]
Abstract
Aptamer-ligand binding has been utilized for biological applications due to its specific binding and synthetic nature. However, the applications will be limited if the binding or the ligand is unstable. Malachite green aptamer (MGA) and its labile ligand malachite green (MG) were found to have increasing apparent dissociation constants (Kd) as determined through the first order rate loss of emission intensity of the MGA-MG fluorescent complex. The fluorescent intensity loss was hypothesized to be from the hydrolysis of MG into malachite green carbinol base (MGOH). Random screening organic additives were found to reduce or retain the fluorescence emission and the calculated apparent Kd of MGA-MG binding. The protective effect became more apparent as the percentage of organic additives increased up to 10% v/v. The mechanism behind the organic additive protective effects was primarily from a ~5X increase in first order rate kinetics of MGOH→MG (kMGOH→MG), which significantly changed the equilibrium constant (Keq), favoring the generation of MG, versus MGOH without organic additives. A simple way has been developed to stabilize the apparent Kd of MGA-MG binding over 24h, which may be beneficial in stabilizing other triphenylmethane or carbocation ligand-aptamer interactions that are susceptible to SN1 hydrolysis.
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Affiliation(s)
- Yubin Zhou
- School of Materials Science & Engineering, College of Engineering, Nanyang Technological University50 Nanyang AvenueSingapore639798Singapore
| | - Hong Chi
- School of Materials Science & Engineering, College of Engineering, Nanyang Technological University50 Nanyang AvenueSingapore639798Singapore
| | - Yuanyuan Wu
- School of Materials Science & Engineering, College of Engineering, Nanyang Technological University50 Nanyang AvenueSingapore639798Singapore
| | - Robert S Marks
- School of Materials Science & Engineering, College of Engineering, Nanyang Technological University50 Nanyang AvenueSingapore639798Singapore; Department of Biotechnology Engineering, Faculty of Engineering Sciences, Ben Gurion University of the NegevP.O. Box 653Beer Sheva84105Israel
| | - Terry W J Steele
- School of Materials Science & Engineering, College of Engineering, Nanyang Technological University50 Nanyang AvenueSingapore639798Singapore.
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Rhinehardt KL, Srinivas G, Mohan RV. Molecular Dynamics Simulation Analysis of Anti-MUC1 Aptamer and Mucin 1 Peptide Binding. J Phys Chem B 2015; 119:6571-83. [PMID: 25963836 DOI: 10.1021/acs.jpcb.5b02483] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Aptasensors utilize aptamers as bioreceptors. Aptamers are highly efficient, have a high specificity and are reusable. Within the biosensor the aptamers are immobilized to maximize their access to target molecules. Knowledge of the orientation and location of the aptamer and peptide during binding could be gained through computational modeling. Experimentally, the aptamer (anti-MUC1 S2.2) has been identified as a bioreceptor for breast cancer biomarker mucin 1 (MUC1) protein. However, within this protein lie several peptide variants with the common sequence APDTRPAP that are targeted by the aptamer. Understanding orientation and location of the binding region for a peptide-aptamer complex is critical in their biosensor applicability. In this study, we investigate through computational modeling how this peptide sequence and its minor variants affect the peptide-aptamer complex binding. We use molecular dynamics simulations to study multiple peptide-aptamer systems consisting of MUC1 (APDTRPAP) and MUC1-G (APDTRPAPG) peptides with the anti-MUC1 aptamer under similar physiological conditions reported experimentally. Multiple simulations of the MUC1 peptide and aptamer reveal that the peptide interacts between 3' and 5' ends of the aptamer but does not fully bind. Multiple simulations of the MUC1-G peptide indicate consistent binding with the thymine loop of the aptamer, initiated by the arginine residue of the peptide. We find that the binding event induces structural changes in the aptamer by altering the number of hydrogen bonds within the aptamer and establishes a stable peptide-aptamer complex. In all MUC1-G cases the occurrence of binding was confirmed by systematically studying the distance distributions between peptide and aptamers. These results are found to corroborate well with experimental study reported in the literature that indicated a strong binding in the case of MUC1-G peptide and anti-MUC1 aptamer. Present MD simulations highlight the role of the arginine residue of MUC1-G peptide in initiating the binding. The addition of the glycine residue to the peptide, as in the case of MUC1-G, is shown to yield a stable binding. Our study clearly demonstrates the ability of MD simulations to obtain molecular insights for peptide-aptamer binding, and to provide details on the orientation and location of binding between the peptide-aptamer that can be instrumental in biosensor development.
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Patra M, Mukhopadhyay C, Chakrabarti A. Malachite green interacts with the membrane skeletal protein, spectrin. RSC Adv 2015. [DOI: 10.1039/c5ra15488j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Energy minimized complex of MG with the self association domain of spectrin.
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Affiliation(s)
- Malay Patra
- Chemistry Department
- University of Calcutta
- Kolkata 700009
- India
| | | | - Abhijit Chakrabarti
- Crystallography & Molecular Biology Division
- Saha Institute of Nuclear Physics
- Kolkata 700064
- India
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11
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Da Costa JB, Andreiev AI, Dieckmann T. Thermodynamics and kinetics of adaptive binding in the malachite green RNA aptamer. Biochemistry 2013; 52:6575-83. [PMID: 23984874 DOI: 10.1021/bi400549s] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Adaptive binding, the ability of molecules to fold themselves around the structure of a ligand and thereby incorporating it into their three-dimensional fold, is a key feature of most RNA aptamers. The malachite green aptamer (MGA) has been shown to bind several closely related triphenyl dyes with planar and nonplanar structures in this manner. Competitive binding studies using isothermal titration calorimetry and stopped flow kinetics have been conducted with the aim of understanding the adaptive nature of RNA-ligand interaction. The results of these studies reveal that binding of one ligand can reduce the ability of the aptamer pocket to adapt to another ligand, even if this second ligand has a significantly higher affinity to the free aptamer. A similar effect is observed in the presence of Mg(2+) ions which stabilize the binding pocket in a more ligand bound-like conformation.
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Affiliation(s)
- Jason B Da Costa
- Department of Chemistry, University of Waterloo , 200 University Ave West, Waterloo, ON N2L3G1, Canada
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12
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Ding F, Li XN, Diao JX, Sun Y, Zhang L, Ma L, Yang XL, Zhang L, Sun Y. Potential toxicity and affinity of triphenylmethane dye malachite green to lysozyme. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2012; 78:41-49. [PMID: 22236952 DOI: 10.1016/j.ecoenv.2011.11.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 10/31/2011] [Accepted: 11/14/2011] [Indexed: 05/31/2023]
Abstract
Malachite green is a triphenylmethane dye that is used extensively in many industrial and aquacultural processes, generating environmental concerns and health problems to human being. In this contribution, the complexation between lysozyme and malachite green was verified by means of computer-aided molecular modeling, steady state and time-resolved fluorescence, and circular dichroism (CD) approaches. The precise binding patch of malachite green in lysozyme has been identified from molecular modeling and ANS displacement, Trp-62, Trp-63, and Trp-108 residues of lysozyme were earmarked to possess high-affinity for this dye, the principal forces in the lysozyme-malachite green adduct are hydrophobic and π-π interactions. Steady state fluorescence proclaimed the complex of malachite green with lysozyme yields quenching through static type, which substantiates time-resolved fluorescence measurements that lysozyme-malachite green conjugation formation has an affinity of 10(3)M(-1). Moreover, via molecular modeling and also CD data, we can safely arrive at a conclusion that the polypeptide chain of lysozyme partially destabilized upon complexation with malachite green. The data emerged here will help to further understand the toxicological action of malachite green in human body.
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Affiliation(s)
- Fei Ding
- Department of Chemistry, China Agricultural University, Beijing 100193, China
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Sokoloski JE, Dombrowski SE, Bevilacqua PC. Thermodynamics of ligand binding to a heterogeneous RNA population in the malachite green aptamer. Biochemistry 2011; 51:565-72. [PMID: 22192051 DOI: 10.1021/bi201642p] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The malachite green aptamer binds two closely related ligands, malachite green (MG) and tetramethylrosamine (TMR), with nearly equal affinity. The MG ligand consists of three phenyl rings emanating from a central carbon, while TMR has two of the three rings connected by an ether linkage. The binding pockets for MG and TMR in the aptamer, known from high-resolution structures, differ only in the conformation of a few nucleotides. Herein, we applied isothermal titration calorimetry (ITC) to compare the thermodynamics of binding of MG and TMR to the aptamer. Binding heat capacities were obtained from ITC titrations over the temperature range of 15-60 °C. Two temperature regimes were found for MG binding: one from 15 to 45 °C where MG bound with a large negative heat capacity and an apparent stoichiometry (n) of ~0.4 and another from 50 to 60 °C where MG bound with a positive heat capacity and an n of ~1.1. The binding of TMR, on the other hand, revealed only one temperature regime for binding, with a more modest negative heat capacity and an n of ~1.2. The large difference in heat capacity between the two ligands suggests that significantly more conformational rearrangement occurs upon the binding of MG than that of TMR, which is consistent with differences in solvent accessible surface area calculated for available ligand-bound structures. Lastly, we note that the binding stoichiometry of MG was improved not only by an increase in the temperature but also by a decrease in the concentration of Mg(2+) or an increase in the time between ITC injections. These studies suggest that binding of a dynamical ligand to a functional RNA requires the RNA itself to have significant dynamics.
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Affiliation(s)
- Joshua E Sokoloski
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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