Biological Interaction of Molybdenocene Dichloride with Bovine Serum

Laboratory Experiment Cite This: J. Chem. Educ. XXXX, XXX, XXX-XXX

pubs.acs.org/jchemeduc

Biological Interaction of Molybdenocene Dichloride with Bovine Serum Albumin Using Fluorescence Spectroscopy Moralba Domínguez, José E. Cortés-Figueroa, and Enrique Meléndez* Department of Chemistry, University of Puerto Rico, P.O. Box 9019, Mayaguez, Puerto Rico 00681, United States S Supporting Information *

ABSTRACT: Bioinorganic topics are ubiquitous in the inorganic chemistry curriculum; however, experiments to enhance understanding of related topics are scarce. In this proposed laboratory, upper undergraduate students assess the biological interaction of molybdenocene dichloride (Cp2MoCl2) with bovine serum albumin (BSA) by fluorescence spectroscopy. Specifically, learners study the quenching mechanism by performing a binding titration of a bovine serum albumin (BSA) solution with molybdenocene dichloride at physiological pH at three temperatures to determine the biomolecular quenching constant as defined in the Stern−Volmer equation. The temperature dependency of the quenching constant allows estimation of thermodynamic parameters which in turn permits an assessment of the nature of the intermolecular interactions involved. This educational activity promotes graph interpretation and integration of concepts such as metallocene−protein interaction, fluorescence quenching, Gibbs energy, entropy, and enthalpy, where students learn to propose a quenching mechanism and to assess the intermolecular forces that may be involved. The proposed experiment can be implemented in various educational settings such as inorganic chemistry, biochemistry, biophysical chemistry, and analytical chemistry. KEYWORDS: Upper-Division Undergraduate, Inorganic Chemistry, Bioinorganic Chemistry, Medicinal Chemistry, Molecular Mechanics/Dynamics, Laboratory Instruction, Hands-On Learning/Manipulatives, Organometallics, Noncovalent Interactions, Thermodynamics

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research groups have demonstrated the existence of the binding interactions of Cp2MoCl2 with DNA, oligonucleotides, and proteins.10−16 One of the transport mechanisms of Cp2MoCl2 and its derivatives into cancer cells involves human serum albumin (HSA). HSA, the most abundant protein in the human blood plasma, is involved in transporting fatty acids, metabolites, and drugs.17 It has been reported that interactions of Cp2MoCl2 and its derivatives with HSA18 most likely involve weak hydrophobic forces.16 Bovine serum albumin (BSA) is a protein isolated from cows, used as an HSA replacing model for biophysical chemistry, biochemistry, and physical chemistry studies due to its high structural (including 3D structure) resemblance (76% to HSA).19−21 Both albumins share 76% sequence homology, and have the same binding sites located on subdomains IIA and IIIA, and the amino acids lining the binding sites are mainly hydrophobic and conserved.19−21 Trp-212 in BSA and Trp-214 in HSA are located in a similar hydrophobic microenvironment

etallocene complexes contain two cyclopentadienyl (Cp) ligands π-bonded to a metal center (see Figure 1). In the past 30 years, the metallocene research has been

Figure 1. Metallocenes with parallel Cp rings (left), M = Fe, Ru, and bent metallocenes (right), M′ = Ti, V, Zr, Nb, Mo, W.

focused toward the development of organometallic anticancer drugs due to their high antiproliferative potential.1,2 The anticancer activity and cytotoxicity of titanocene, molybdenocene, vanadocene, ferrocene, zirconocene, tungstenocene, and their derivatives have been reported.3−6 The anticancer properties, hydrolysis, and stability at physiological pH of molybdenocene dichloride (Cp2MoCl2) make it an excellent model to design antineoplastic agents.7−9 Binding interactions are used to assess the mechanisms of transport, distribution, and metabolism of drugs. Various © XXXX American Chemical Society and Division of Chemical Education, Inc.

Received: March 5, 2017 Revised: September 18, 2017

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DOI: 10.1021/acs.jchemed.7b00178 J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

Laboratory Experiment

2 mL jacketed cuvette. A detailed protocol description is available in the Supporting Information.

in subdomain IIA and are used as probes to monitor drug binding interactions within the albumin.22 The nature of protein−ligand interactions can be determined by a variety of techniques such as UV−vis spectrophotometry, fluorescence spectroscopy, circular dichroism (CD), Fourier transform infrared spectroscopy (FT-IR), cyclic voltammetry, nuclear magnetic resonance (NMR), and molecular docking. The fluorescence technique should be particularly valuable in a teaching setting because it can be easily adapted for a chemistry laboratory course. For example, the BSA−metallocene interactions can be monitored by fluorescence spectroscopy because this protein’s emission intensity comes from the aromatic amino acids, tryptophan (Trp), tyrosine (Tyr), and phenylalanine (Phe), which upon binding decrease their emission intensity. Particularly, Trp-212 and Trp-13422 (see Figure 2) dominate the BSA fluorescence, and their emission

Determination of Quenching Constants and Thermodynamic Parameters

Once the students identify the maximum of the fluorescence spectra (intensity vs wavelength plots), they proceed to determine F0/F ratios at each temperature. With the Stern− Volmer equation (eq 1) the following abbrevations are used: F0 and F are the fluorescence intensity of BSA in absence and presence of the quencher (Cp2MoCl2), respectively, [Q] is the quencher concentration, τ0 is the fluorescence average lifetime of the unquenched molecule (for a biopolymer, it is given as 10−8 s−1), kq is the quenching rate constant, and Ksv is the Stern−Volmer quenching constant (Ksv = kqτ0). Once F0/F ratios are determined, the students construct Stern−Volmer plots (F0/F vs [Q]), which, according to eq 1, are expected to be linear with a slope equal to Ksv. F0 = 1 + kqτ0[Q] = 1 + K sv[Q] F

(1)

The thermodynamic parameters ΔH° and ΔS° are estimated from the ln Ksv versus 1/T plot as predicted by the van’t Hoff equation (eq 2), where R is the ideal gas constant, T is the absolute temperature, and Ksv is the quenching constant, which is analogous to kq at the corresponding temperature T. In the case of a static quenching mechanism, the interpretation is that this constant can be regarded as a binding constant.25,26,29 The corresponding ΔG° values at temperature T are estimated from ΔG° = ΔH° + TΔS°. These thermodynamic parameters in turn are used to propose a mechanistic description of the BSA− Cp2MoCl2 binding interaction.

Figure 2. Structure of bovine serum albumin with fluorescent tryptophan residues.

ln K sv = −

intensity may be affected by molecular interactions. This expectation prompted the design of an experiment for the inorganic chemistry laboratory, where BSA binding interactions with molybdenocene dichloride (Cp2MoCl2) are monitored by fluorescence spectroscopy. It is expected that, in this proposed experiment, students will integrate concepts related to organometallic chemistry, bioinorganic chemistry, biochemistry, biophysical chemistry, analytical chemistry, and physical chemistry.

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ΔH ° ΔS° + RT R

(2)

HAZARDS Safety glasses, gloves, and laboratory coats should be worn at all times during this experiment. Molybdenocene dichloride (bis(cyclopentadienyl)molybdenum(IV) dichloride) may cause skin, respiratory, and eye irritation. Molybdenocene dichloride waste should be disposed by a licensed disposal company. Bovine serum albumin and trizma base are not particularly hazardous substances or mixtures. Sodium hydroxide and hydrochloric acid are dangerous, and can cause severe skin burns and serious eye damage.

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EXPERIMENTAL PROCEDURE This experiment has been performed by about 60 students in six sections of the Inorganic Chemistry Laboratory at University of Puerto RicoMayaguez campus. The expected time to complete this experiment is approximately 4 h. Typically, this laboratory activity was distributed among the students, who formed groups of three or four students each. Once the experiment was completed, the instructor collected the data from each group and shared it with all the students involved for individual analysis and for a report of the results in a journal’s style. Students are expected to prepare most of the required solutions. In a typical experiment, a BSA solution (1 mL, ca. 1.8 × 10−6 M, Tris 0.1 M, pH 7.4) is titrated with successive 15 μL aliquots of molybdenocene dichloride solutions (3.4 mM, Tris 0.1 M, pH 7.4). The quenching progress is monitored by recording the fluorescence spectra at 280 nm, at an emission range 300−400 nm. These spectra are obtained at three temperatures (ca. 30, 37, and 44 °C) using a spectrofluorophotometer equipped with a temperature control device and a

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RESULTS AND DISCUSSION The proposed experiment has been used as part of the experiments of the upper-division inorganic chemistry laboratory at UPRM. Approximately 60 students in various sections have completed the experiment. The experimental details are presented in the Supporting Information section. Students’ understanding of the concepts are assessed with a prelaboratory test, a journal style laboratory report, and a final laboratory test. Also, students are instructed in a prelaboratory section about pertinent concepts, calculations, preparation of samples, and the proper use of the fluorescence spectrophotometer. In the past 10−15 years, topics such as bioinorganic chemistry, materials chemistry, nanoscience, and new trends in organometallic chemistry have been included within the undergraduate inorganic chemistry courses.23 This laboratory practice integrates most of these concepts. Because this B




experiment is based on research articles reporting on the Cp2MCl2 (M = Mo, W)−protein interactions6,13,16,18 and BSA−ligand interactions evaluated by fluorescence spectroscopy,19,24−26 its reflects a “real world” setting, where students are encouraged to perform literature research before they are engaged in actual laboratory practice. This type of metallocene−protein interaction was, for the first time, reported by our group and described how a metallocene is transported in the serum into the target place in the cell and how the amino acids engaged in bonding with the metallic drug.6,13,16,18 This is a fundamental aspect about the mechanism of action and transport of these metallocenes which is currently of interest in bioorganometallic chemistry. The fluorescence intensity of a protein can be affected by excitations to higher states, molecular rearrangements, energy transfer, complex formation, or collisions leading to fluorescence quenching. The titration fluorescence spectra of BSA with Cp2MoCl2 at 44 °C are shown in Figure 3. The system

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Figure 4. Stern−Volmer plots ( F0 vs [Cp2MoCl 2]) for BSA− [Cp2MoCl2] interaction at various temperatures: black 303 K, blue 310 K, purple 317 K.

Table 1. Stern−Volmer Equations and Quenching Constants at Different Temperatures T/K

Stern−Volmer Equationa

Ksv/(L/mol)a

kq/(L/mol s)a

303

F0/F = 1.20(5) × 10 [Q] + 0.986(8) F0/F = 1.33(4) × 103[Q] + 0.991(6) F0/F = 1.76(6) × 103[Q] + 0.983(9)

1.20(5) × 10

1.20(5) × 1011

310 317

3

3

1.33(4) × 103

1.33(4) × 1011

1.76(6) × 103

1.76(6) × 1011

a

The digit(s) in parentheses corresponds to the uncertainty of the last digit.

Table 2. Thermodynamic Parameters of BSA−Cp2MoCl2 Interaction at Various Temperatures

Figure 3. Fluorescence quenching spectra during the titration of BSA with Cp2MoCl2 at 317 K.

exhibits a strong fluorescence emission band at 336 nm, the intensity of which decreases with the Cp2MoCl2 concentration due to changes in the Trp-212 environment.6,19−22 The quenching mechanism parameters of this interaction can be determined from the Stern−Volmer plot (Figure 4). Analysis of Stern−Volmer linear plots suggests the existence of a single quenching mechanism, either static or dynamic.27 Table 1 shows that Ksv values increase with temperature. This trend, together with the observation that kq values are larger than the limiting diffusion collision quenching constant, kD, of a biomolecule with various quenchers (2 × 1010 M−1 s−1), indicates that a static quenching mechanism is operative.28,29 Table 2 shows thermodynamic parameters at various temperatures calculated from the van’t Hoff equation (eq 2). Figure 5 shows this plot and its regression equation

T/K

ΔH°/(kJ/mol)a

ΔS°/(J/mol)a

ΔG°/(kJ/mol)a

303 310 317

22(6) 22(6) 22(6)

130(16) 130(16) 130(16)

−17(8) −18(8) −19(8)

a

The digit(s) in parentheses corresponds to the uncertainty of the last digit.

the Cp rings with the Trp and the hydrophobic pocket of the protein. One should mention that the metal center and not the Cp rings is the part that imparts anticancer activity to the complex. The proposed mechanism of action is where the metal center interacts with the phosphates of DNA bases as well as inhibits protein kinase C (PKC) and tubulin, inhibiting cell proliferation and as a result eliciting its anticancer activity.7 The BSA’s fluorescence comes from Trp-212 and Trp-134. Because Trp-212 is located inside of a hydrophobic pocket of the BSA and Trp-134 is located on the surface of a hydrophilic region (see Figure 2), the change of the fluorescence intensity is ascribed mainly to Cp2MoCl2−Trp-212 binding. This result is consistent with the description of the interaction of Cp2MoCl2 with HSA suggested by Feliciano et al.16 Furthermore, results from other studies where the interactions of HSA with a variety of organometallic compounds were monitored using fluorescence spectroscopy support that hydrophobic interaction is the main binding mode.6,31 In addition, it has been suggested that metallic centers can interact weakly with HSA through the

2.6(7) × 103

+ 16(2)). Microscopic details of the (ln K sv = T interactions that may be involved such as hydrophobicity and the type of bonding interactions (van der Waals, hydrogen bonding, electrostatic, or ionic) can be deduced from the thermodynamic parameters. For example, the values ΔG° < 0 listed in Table 2 indicate that the BSA−molybdenocene interaction is a spontaneous process, where the main binding forces are hydrophobic interactions because ΔH° and ΔS° exhibit positive values.30 Hydrophobic interactions arise from C




Figure 5. van’t Hoff plot of BSA−Cp2MoCl2 interaction at different temperatures. Slope = 2.6(7) × 103; intercept = 16(2). The digit in parentheses corresponds to the uncertainty of the last digit(s).

Figure 6. Linear plot of ΔH° vs ΔS° for protein−ligand association showing the existence of a compensation effect and supporting that each set of binding processes takes place via a common mechanism. The ΔH and ΔS values used to construct these plots were taken from tables II of ref 30.

indole ring on the Trp-212, promoting hydrophobic interactions in a manner analogous to the DNA−Mo and DNA−Ru binding mode where the metal−DNA binding takes place through a guanine residue.31,32 The instructors of this laboratory at UPRM encourage students to search the chemical literature for thermodynamic parameters of closely related protein−ligand binding interactions to suggest a mechanistic interpretation of the thermodynamic parameters obtained in the laboratory, concurrently performing assessment, via discussions, of the students’ conceptual understanding of the parameters. For example, assessment of the students’ conceptual understanding of these parameters shows that most of them are able to relate ΔG° < 0 values to spontaneous binding processes. However, they tend to fail to recognize that when a pair of ΔH° and ΔS° values differ within the various systems, the spontaneous binding processes may proceed via a common mechanism. This situation prompted vivid discussions among the professors and teaching assistants that teach this laboratory at UPRM. The consensus among the professors and instructors was to introduce a concept analogous to isokinetic relationships,33 where processes that take place via a common general mechanism are expected to exhibit a compensation between ΔH° and ΔS° values in such a way that plots of ΔH° versus ΔS° should be linear where the slope of the plot is the “isotemperature” (Tiso) where for all binding processes within the system of reactions, the binding rate constant will have a same value. Figure 6 shows a linear plot for a protein−ligand binding system reported in the literature.30 In addition, it is expected that if Tiso exists, then ln Ksv versus 1/T plots for binding processes operating via a common mechanism will show a tendency toward a common intersection point or region at Tiso (Figure 7). The temperature at which this common intersection point or region is observed is Tiso. Typically students are requested to compare Ksv values at both sides of Tiso, noticing that Tiso is an inversion point with respect to the relative Ksv values. Therefore, students and researchers alike should recognize the existence of this isotemperature relationship when using Ksv values to describe mechanistically binding interactions. Furthermore, postlaboratory discussions should use Figure 7 to address the concept of “enthalpy driven”/“entropy driven” binding processes by

Figure 7. van’t Hoff plots for protein−ligand association, suggesting the existence of a Tiso region. These plots were constructed with ln K values at temperature T calculated using eq 2 and ΔH and ΔS values taken from Table 2 of ref 30.

showing that to the left of the Tiso point (relative large temperatures) the binding is entropy driven, while to the right of the point (relative small temperatures) the binding process is enthalpy driven. Another important aspect in the postlaboratory discussions is that comparison of Ksv constant values for binding processes may lack interpretative value if Tiso is unknown. For example, if Ksv values are inadvertently evaluated in the proximity of Tiso, then Ksv values may be independent of the forces that are operating in the binding process. However, the Tiso for these types of processes (using Figure 6) is in the vicinity of 243(17) K. Thus, our experimentation is in the low temperature region which is mostly enthalpy driven and supports the hydrophobic interactions.

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CONCLUSIONS This laboratory practice integrates a variety of biological, bioinorganic, and physical chemical concepts. It promotes D




Derivatives of the Antitumor Agent Molybdocene Dichloride. J. Med. Chem. 2005, 48 (6), 2093−2099. (9) Gleeson, B.; Claffey, J.; Deally, A.; Hogan, M.; Mendez, L. M. M.; Muller-Bunz, H.; Patil, S.; Tacke, M. Novel Benzyl-Substituted Molybdocene Anticancer Drugs. Inorg. Chim. Acta 2010, 363 (8), 1831−1836. (10) Vera, J. L.; Roman, F. R.; Melendez, E. Study of TitanoceneDNA and Molybdenocene-DNA Interactions by Inductively Coupled Plasma-Atomic Emission Spectroscopy. Anal. Bioanal. Chem. 2004, 379 (3), 399−403. (11) Harding, M. M.; Mokdsi, G.; Mackay, J. P.; Prodigalidad, M.; Lucas, S. W. Interactions of the Antitumor Agent Molybdocene Dichloride with Oligonucleotides. Inorg. Chem. 1998, 37 (10), 2432− 2437. (12) Kuo, L. Y.; Kanatzidis, M. G.; Sabat, M.; Tipton, A. L.; Marks, T. J. Metallocene Antitumor Agents. Solution and Solid-State Molybdenocene Coordination Chemistry. J. Am. Chem. Soc. 1991, 113 (24), 9027−9045. (13) Narvaez-Pita, X.; Ortega-Zuniga, C.; Acevedo-Morantes, C. Y.; Pastrana, B.; Olivero-Verbel, J.; Maldonado-Rojas, W.; Ramirez-Vick, J. E.; Melendez, E. Water Soluble Molybdenocene Complexes: Synthesis, Cytotoxic Activity and Binding Studies to Ubiquitin by Fluorescence Spectroscopy, Circular Dichroism and Molecular Modeling. J. Inorg. Biochem. 2014, 132, 77−91. (14) Vera, L.; Roman, R.; Melendez, E. Molybdenocene − Oligonucleotide Binding Study at Physiological pH Using NMR Spectroscopy and Cyclic Voltammetry. Bioorg. Med. Chem. 2006, 14 (24), 8683−8691. (15) Rodriguez, M. I.; Chavez-Gil, T.; Colon, Y.; Diaz, N.; Melendez, E. Molybdenocene − DNA Interaction Studies Using Electrochemical Analysis. J. Electroanal. Chem. 2005, 576 (2), 315−322. (16) Feliciano, I.; Matta, J.; Melendez, E. Water-Soluble Molybdenocene Complexes with Both Proliferative and Antiproliferative Effects on Cancer Cell Lines and Their Binding Interactions with Human Serum Albumin. JBIC, J. Biol. Inorg. Chem. 2009, 14 (7), 1109−1117. (17) Curry, S.; Mandelkow, H.; Brick, P.; Franks, N. Crystal Structure of Human Serum Albumin Complexed with Fatty Acid Reveals an Asymmetric Distribution of Binding Sites. Nat. Struct. Biol. 1998, 5 (9), 827−835. (18) Campbell, K. S.; Dillon, C. T.; Smith, S. V.; Harding, M. M. Radiotracer Studies of the Antitumor Metallocene Molybdocene Dichloride with Biomolecules. Polyhedron 2007, 26 (2), 456−459. (19) Bourassa, P.; Kanakis, C. D.; Tarantilis, P.; Pollissiou, M. G.; Tajmir-Riahi, H. A. Resveratrol, Genistein, and Curcumin Bind Bovine Serum Albumin. J. Phys. Chem. B 2010, 114 (9), 3348−3354. (20) Shi, J.; Pan, D.; Wang, X.; Liu, T.-T.; Jiang, M.; Wang, Q. Characterizing the Binding Interaction between Antimalarial Artemether (AMT) and Bovine Serum Albumin (BSA): Spectroscopic and Molecular Docking Methods. J. Photochem. Photobiol., B 2016, 162, 14−23. (21) Roy, S.; Nandi, R. K.; Ganai, S.; Majumdar, K. C.; Das, T. K. Binding Interaction of Phosphorus Heterocycles with Bovine Serum Albumin: A Biochemical Study. J. Pharm. Anal. 2017, 7, 19−26. (22) Tayeh, N.; Rungassamy, T.; Albani, J. R. Fluorescence Spectral Resolution of Tryptophan Residues in Bovine and Human Serum Albumins. J. Pharm. Biomed. Anal. 2009, 50 (2), 107−116. (23) Raker, J. R.; Reisner, B. A.; Smith, S. R.; Stewart, J. L.; Crane, J. L.; Pesterfield, L.; Sobel, S. G. Foundation Coursework in Undergraduate Inorganic Chemistry: Results from a National Survey of Inorganic Chemistry Faculty. J. Chem. Educ. 2015, 92 (6), 973−979. (24) Liu, P.; Liu, Y.; Wang, Q. Studies on the Interaction of CdTe QDs with Bovine Serum Albumin. J. Chem. Technol. Biotechnol. 2012, 87 (12), 1670−1675. (25) Xiao, C.-Q.; Jiang, F.-L.; Zhou, B.; Li, R.; Liu, Y. Interaction between a Cationic Porphyrin and Bovine Serum Albumin Studied by Surface Plasmon Resonance, Fluorescence Spectroscopy and Cyclic Voltammetry. Photochem. Photobiol. Sci. 2011, 10 (7), 1110−1117.

connection of concepts via graph construction and interpretation. Graph analysis and interpretation of information searched in the scientific literature promote development of analytical and critical thinking skills among students. It also offers a laboratory experience where students explore a scientific problem in a research-like manner. In our opinion students were more engaged in the learning process when this biological application of inorganic chemistry was used as a teaching tool. This is a versatile and easy to perform experiment that can be adopted in a variety of courses such as biochemistry, biophysical chemistry, and analytical chemistry.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.7b00178. Student handout (PDF, DOCX) Instructor notes (PDF, DOCX)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Enrique Meléndez: 0000-0002-8466-6170 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors gratefully acknowledge the helpful comments and participation of the UPRM undergraduate students of the inorganic laboratory course (QUIM-4007L). We are grateful to UPRM Chemistry Department for financial support. E.M. acknowledges the financial support of Héctor Collazo, Esq., for the funds provided through the International Health Games.

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REFERENCES

(1) Meléndez, E. Metallocenes as Target Specific Drugs for Cancer Treatment. Inorg. Chim. Acta 2012, 393, 36−52. (2) Albada, B.; Metzler-Nolte, N. Organometallic−Peptide Bioconjugates: Synthetic Strategies and Medicinal Applications. Chem. Rev. 2016, 116 (19), 11797−11839. (3) Gomez-Ruiz, S.; Maksimovic-Ivanic, D.; Mijatovic, S.; Kaluderovic, G. On the Discovery, Biological Effects, and Use of Cisplatin and Metallocenes in Anticancer Chemotherapy. Bioinorg. Chem. Appl. 2012, 2012, 1. (4) Gasser, G.; Ott, I.; Metzler-Nolte, N. Organometallic Anticancer Compounds. J. Med. Chem. 2011, 54 (1), 3−25. (5) Vessières, A.; Plamont, M.; Cabestaing, C.; Claffey, J.; Dieckmann, S.; Hogan, M.; Müller-bunz, H.; Strohfeldt, K.; Tacke, M. Proliferative and Anti-Proliferative Effects of Titanium- and IronBased Metallocene Anti-Cancer Drugs. J. Organomet. Chem. 2009, 694 (6), 874−879. (6) Domínguez-García, M.; Ortega-Zúñiga, C.; Meléndez, E. New Tungstenocenes Containing 3-Hydroxy-4-Pyrone Ligands: Antiproliferative Activity on HT-29 and MCF-7 Cell Lines and Binding to Human Serum Albumin Studied by Fluorescence Spectroscopy and Molecular Modeling Methods. JBIC, J. Biol. Inorg. Chem. 2013, 18 (2), 195−209. (7) Melendez, E. Bioorganometallic Chemistry of Molybdenocene Dichloride and Its Derivatives. J. Organomet. Chem. 2012, 706, 4−12. (8) Waern, J. B.; Dillon, C. T.; Harding, M. M. Organometallic Anticancer Agents: Cellular Uptake and Cytotoxicity Studies on Thiol E




(26) Ye, H.; Qiu, B.; Lin, Z.; Chen, G. Fluorescence Spectrometric Study on the Interactions of Tamibarotne with Bovine Serum Albumin. Luminiscence 2011, 26 (5), 336−341. (27) Lakowicz, J. R. Principles of Fluorescence Spectroscopy, 3rd ed.; Springer US: Baltimore, MD, 2006; pp 278−292. (28) Ware, W. R. Oxygen Quenching of Fluorescence in Solution: An Experimental Study of the Diffusion Process. J. Phys. Chem. 1962, 66 (3), 455−458. (29) Papadopoulou, A.; Green, R. J.; Frazier, R. A. Interaction of Flavonoids with Bovine Serum Albumin: A Fluorescence Quenching Study. J. Agric. Food Chem. 2005, 53, 158−163. (30) Ross, P. D.; Subramanian, S. Thermodynamics of Protein Association Reactions: Forces Contributing to Stability. Biochemistry 1981, 20 (11), 3096−3102. (31) Beckford, F.; Dourth, D.; Shaloski, M.; Didion, J.; Thessing, J.; Woods, J.; Crowell, V.; Gerasimchuk, N.; Gonzalez-Sarrías, A.; Seeram, N. P. Half-Sandwich Ruthenium-Arene Complexes with Thiosemicarbazones: Synthesis and Biological Evaluation of [(η6-P-cymene)Ru(piperonal thiosemicarbazones)Cl]Cl Complexes. J. Inorg. Biochem. 2011, 105 (8), 1019−1029. (32) Lopez-Ramos, V.; Vega, C. A.; Cadiz, M.; Meléndez, E. Electrochemical and Spectroscopic Analysis of the Interaction of Molybdenocene Dichloride with Nitrogen Bases. J. Electroanal. Chem. 2004, 565, 77−83. (33) Espenson, J. H. Chemical Kinetics and Reaction Mechanisms, 2nd ed.; Mc Graw-Hill: New York, 1995; p 164.

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Biological Interaction of Molybdenocene Dichloride with Bovine Serum

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