Synthesis of a 5-Carboxy Indole-Based Spiropyran Fluorophore: Thermal, Electrochemical, Photophysical and Bovine Serum Albumin Interaction Investigations
, Daniela Brondani 3, Eduardo Zapp 3, Paulo Fernando Bruno Gonçalves 2, Fabiano Severo Rodembusch 2,* and Alexandre Gonçalves Dal-Bó 1,*
Round 1
Reviewer 1 Report
The article entitles
Synthesis of a 5-carboxy indole-based spiropyran fluorophore: Thermal, electrochemical, photophysical and bovine serum albumin interaction investigations is of interest for the scientific community. The article is well structured but I will suggest to the authors:
- to perform the MS of the compound.
- Can the authors specify the purity of the compund
- to control the experimental part and to verify the weight of each reagent
Author Response
Reviewer #1
The article entitles Synthesis of a 5-carboxy indole-based spiropyran fluorophore: Thermal, electrochemical, photophysical and bovine serum albumin interaction investigations is of interest for the scientific community. The article is well structured but I will suggest to the authors:
- to perform the MS of the compound.
- Can the authors specify the purity of the compound
- to control the experimental part and to verify the weight of each reagent
Answer. Thanks for the comments. Concerning the two initial comments, usually it is presented to new compounds or HRMS or the elemental analysis. The NMR results clearly indicate that no evidence of the precursors could be found in the NMR data. The same can be observed in the UV-Vis Spectra. However, we would like to highlight that at this point, both characterizations are already in progress since early April. Nevertheless, after the COVID-19 all spectroscopic techniques are no longer available at all universities and research centers here in our country. So, although we do not have this data, in order to respect the deadline of 5 days to submit the revised version of the manuscript, we decided to send without this characterization. We hope that the reviewer or the editor give us additional time, (we don't know how long we won't have access to spectroscopic techniques) or accept the revision with the spectroscopic characterization.
Finally, the weight of each reagent was verified and corrected, as requested.
Reviewer 2 Report
The manuscript represents a comprehensive research on synthesis, electrochemical, thermal and photophysical characterisation of a novel 5-carboxy indole-based spiropyran fluorophore. The interaction of the fluorophore with bovine serum albumin, BSA, as a protein analyte example was studied and confirmed by theoretical DFT calculations. The work is well written, contains representative references and conclusions supported by results. I would like to recommend the manuscript for publication in Chemosensors in present form.
Author Response
Reviewer #2
The manuscript represents a comprehensive research on synthesis, electrochemical, thermal and photophysical characterisation of a novel 5-carboxy indole-based spiropyran fluorophore. The interaction of the fluorophore with bovine serum albumin, BSA, as a protein analyte example was studied and confirmed by theoretical DFT calculations. The work is well written, contains representative references and conclusions supported by results. I would like to recommend the manuscript for publication in Chemosensors in present form.
Answer. Thanks for the evaluation of this manuscript
Reviewer 3 Report
Current manuscript describes the development of a spiropyran-based fluorophore including an electron-withdrawing carboxyl at position 5, as well as the study of its thermal, electrochemical and photophysical properties.
I consider that the results reported are suitable for publication in Chemosensors.
Minor remarks:
The introduction on spiropyrans should be increased providing more references.
Page 4, line 141: The detailed synthetic procedures of the different steps to obtain the compound 7 should be included in the Supporting Information. Moreover, an experimental evidence (M.p. RMN…) of having synthesized 3 and 5 should be provided.
Page 4, Scheme 2 should include yields of all the steps.
Page 4, line 150: The number of the cis protons should be included.
Page 8, line 242: A deeper explanation on the absence of the open form should be provided, including some references.
Page 8, table 2: All the details of the different parameters should be included in the footer of the table.
Page 9, line 271: A deeper explanation on the calculation of the ionization constants should be provided.
Author Response
Reviewer #3
The current manuscript describes the development of a spiropyran-based fluorophore including an electron-withdrawing carboxyl at position 5, as well as the study of its thermal, electrochemical and photophysical properties. I consider that the results reported are suitable for publication in Chemosensors.
Minor remarks:
The introduction on spiropyrans should be increased providing more references.
Page 4, line 141: The detailed synthetic procedures of the different steps to obtain the compound 7 should be included in the Supporting Information. Moreover, an experimental evidence (M.p. RMN…) of having synthesized 3 and 5 should be provided.
Answer. Thanks for the comments. Concerning the first suggestion, the introduction on spiropyrans was rewrite and additional references were added to the two initial sentences in the revised version of the manuscript.
The second comment was also accepted and the detailed synthetic procedure of the different steps to obtain the compound 7 were included in the Supporting Information. We would like to highlight, as discussed in the manuscript, that the precursors 3 and 5 are not new, are already described in the literature and only the last compound is innovative. To clarify this topic, the respective references were these compounds were firstly described are presented now in the revised version of the manuscript.
Page 4, Scheme 2 should include yields of all the steps.
Answer. Thanks for the comment. We accepted the suggestion. Changes were performed in the revised version of the manuscript.
Page 4, line 150: The number of the cis protons should be included.
Answer. Thanks for the comment. We accepted the suggestion. Changes were performed in the revised version of the manuscript.
Page 8, line 242: A deeper explanation on the absence of the open form should be provided, including some references.
Answer. Thanks for the comment. Changes were performed in the revised version of the manuscript. To clarify this topic, the sentence "No evidence of an open form could be observed, in contrast with the spectra of compounds that have a nitro group [54]. This result may be related to the absence of the electron-withdrawing nitro group that cannot stabilize the generated phenolate as a weak base." was rewrite. In addition, this topic in the results and discussion section was reorganized for better understanding.
Page 8, table 2: All the details of the different parameters should be included in the footer of the table.
Answer. Thanks for the comment. We accepted the suggestion. Changes were performed in the revised version of the manuscript.
Page 9, line 271: A deeper explanation on the calculation of the ionization constants should be provided.
Answer. Thanks for the comment. The discussion about the calculation of the ionization constants was improved; however, we could not understand the essence of this suggestion, since our discussion was performed as usually can be found in the literature (please see some examples: Phys. Chem. Chem. Phys. 2003, 5, 461; Phys. Chem. Chem. Phys. 2012, 14, 2292; New J. Chem. 2003, 27, 1336; J. Phys. Chem. 1993, 97, 2618; J. Photochem. Photobiol. A Chem. 1999, 122, 151; J. Photochem. Photobiol. A Chem. 1994, 78, 127; Anal. Chem. 1986, 58, 612; J. Chem. Eng. Data, 2013, 58, 1706; J. Mol. Struct. 2003, 626, 167; J. Chem. Eng. Data, 2010, 55, 1153; Asian J. Chem. 2008, 20, 3569; Asian J. Chem. 2009, 21, 1453; Langmuir, 2013, 29, 448), both in materials and methods section, as well as in the Results and discussion one. Please, if we are missing something here, let us know.
