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Publications (4 of 4) Show all publications
Osella, S., Di Meo, F., Natarajan Arul, M., Fabre, G., Ameloot, M., Trouillas, P. & Knippenberg, S. (2018). Combining (Non)linear Optical and Fluorescence Analysis of DiD To Enhance Lipid Phase Recognition. Journal of Chemical Theory and Computation, 14(10), 5350-5359
Open this publication in new window or tab >>Combining (Non)linear Optical and Fluorescence Analysis of DiD To Enhance Lipid Phase Recognition
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2018 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 14, no 10, p. 5350-5359Article in journal (Refereed) Published
Abstract [en]

The widespread interest in phase recognition of lipid membranes has led to the use of different optical techniques to enable differentiation of healthy and not fully functional cells. In this work, we show how the combination of different (non)linear optical methods such as one-photon absorption (OPA), two-photon absorption (TPA), and second harmonic generation (SHG) as well as the study of the fluorescence decay time leads to an enhanced screening of membrane phases using a fluorescent 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine (DiD) probe. In the current study we consider the pure liquid disordered phases of DOPC (dioleoyl-sn-glycero-3-phosphocholine, room temperature) and DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 323 K), the solid gel phase of DPPC (298 K), and the liquid ordered phase of a 2:1 binary mixture of sphingomyelin and cholesterol. By means of extensive hybrid quantum mechanics molecular mechanics calculations and based upon the (non)linear absorption of the embedded probes, it is found that DiD can be used to identify the lipid bilayer phase. The joint TPA and SHG as well as fluorescence analyses qualifies DiD as a versatile probe for phase recognition. In particular, the SHG data obtained by means of hyper-Rayleigh scattering and by electric field induced second harmonic generation reveal differences in polarization of the probe in the different environments. The TPA results finally confirm the particular location of the probe in between the polar headgroup region of the 2:1 SM:Chol mixture in the liquid ordered phase.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-238130 (URN)10.1021/acs.jctc.8b00553 (DOI)000447238500031 ()30216061 (PubMedID)2-s2.0-85054346528 (Scopus ID)
Note

QC 20181113

Available from: 2018-11-13 Created: 2018-11-13 Last updated: 2018-11-13Bibliographically approved
Osella, S. & Knippenberg, S. (2017). Triggering On/Off States of Photoswitchable Probes in Biological Environments. Journal of the American Chemical Society, 139(12), 4418-4428
Open this publication in new window or tab >>Triggering On/Off States of Photoswitchable Probes in Biological Environments
2017 (English)In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, no 12, p. 4418-4428Article in journal (Refereed) Published
Abstract [en]

The use of hybrid systems for which the change in properties of one component triggers the change in properties of the other is of outmost importance when "on/off' states are needed. For such a reason, azobenzene compounds are one of the most used probes due to their high photoswitching efficiency. In this study, we consider a new derivative of azobenzene interacting with different lipid membrane phases as a versatile fluorescent probe for phase recognition. By means of a multiscale approach, we found that the cis and trans conformers have different positions and orientations in the different lipid membranes (DOPC for the liquid disordered phase and DPPC for the gel phase), and these have a profound effect on the optical properties of the system, for both one and two photon absorption. In fact, we found that the cis state is the "on" state when the probe is inserted into the DOPC membrane, while it is in the "off' state in the DPPC membrane. This behavior enhances the selectivity of this probe for phase recognition, since the different environments will generate different responses on the same conformer of the probe. The same effect is found for the fluorescence anisotropy analysis, for which the trans (cis) isomer in DOPC (DPPC) presents a fast decay time. Due to the "on/off' effect it is possible to screen the different membrane phases via fluorescence decay time analysis, making this new probe versatile for phase detection.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-205450 (URN)10.1021/jacs.6b13024 (DOI)000398247100038 ()28252300 (PubMedID)2-s2.0-85016257716 (Scopus ID)
Note

QC 20170523

Available from: 2017-05-23 Created: 2017-05-23 Last updated: 2017-06-30Bibliographically approved
Osella, S., Minoia, A. & Beljonne, D. (2016). Combined Molecular Dynamics and Density Functional Theory Study of Azobenzene-Graphene Interfaces. The Journal of Physical Chemistry C, 120(12), 6651-6658
Open this publication in new window or tab >>Combined Molecular Dynamics and Density Functional Theory Study of Azobenzene-Graphene Interfaces
2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 12, p. 6651-6658Article in journal (Refereed) Published
Abstract [en]

The electronic properties of graphene can be tuned in a dynamic way from physical adsorption of molecular photoswitches. Here, we first investigate the formation of 4-(decyloxy)azobenzene molecular monolayers on a single graphene layer through molecular dynamics (MD) simulations and assess the associated change in work function (WF) at the density functional theory (DFT) level. We show that the major contribution to the WF shift arises from electrostatic effects induced by the azobenzene electric dipole component normal to graphene and that the conformational distribution of the molecular switches in either their trans or cis forms can be convoluted into WF distributions for the hybrid systems. We next use this strategy to build a statistical ensemble for the work functions of graphene decorated with fluorinated azobenzene derivative designed to maximize the change in WF upon photoswitching. These findings pave the way to the possible use of photoswitchable graphene-based hybrid materials as optically controlled memories for light-assisted programming and high-sensitive photosensors.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-185996 (URN)10.1021/acs.jpcc.6b00393 (DOI)000373416500041 ()2-s2.0-84963791299 (Scopus ID)
Note

QC 20160510

Available from: 2016-05-10 Created: 2016-04-29 Last updated: 2017-11-30Bibliographically approved
Osella, S., Murugan, N. A., Jena, N. K. & Knippenberg, S. (2016). Investigation into Biological Environments through (Non)linear Optics: A Multiscale Study of Laurdan Derivatives. Journal of Chemical Theory and Computation, 12(12), 6169-6181
Open this publication in new window or tab >>Investigation into Biological Environments through (Non)linear Optics: A Multiscale Study of Laurdan Derivatives
2016 (English)In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 12, no 12, p. 6169-6181Article in journal (Refereed) Published
Abstract [en]

The fluorescent marker Laurdan and its new derivative, C-Laurdan, have been investigated by means of theoretical calculations in a DOPC lipid bilayer membrane at room temperature, and a comparison is made with results from fluorescence experiments. Experimentally, the latter probe is known to have a higher sensitivity to the membrane polarity at the lipid headgroup region and has higher water solubility. Results from Molecular Dynamics (MD) simulations show that C-Laurdan is oriented with the carboxyl group toward the head of the membrane, with an angle of 50 degrees between the molecular backbone and the normal to the bilayer, in contrast to the orientation of the Laurdan headgroup whose carbonyl group is oriented toward the polar regions of the membrane and which describes an angle of ca. 70-80 degrees with the membrane normal. This contrast in orientation reflects the differences in transition dipole moment between the two probes and, in turn, the optical properties. QM/MM results of the probes show little differences for one- (OPA) and two-photon absorption (TPA) spectra, while the second harmonic generation (SHG) beta component is twice as large in Laurdan with respect to C-Laurdan probe. The fluorescence anisotropy decay analysis of the first excited state confirms that Laurdan has more rotational freedom in the DOPC membrane, while C-Laurdan experiences a higher hindrance, making it a better probe for lipid membrane phase recognition.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-199503 (URN)10.1021/acs.jctc.6b00906 (DOI)000389866500041 ()2-s2.0-85006010884 (Scopus ID)
Note

QC 20170117

Available from: 2017-01-17 Created: 2017-01-09 Last updated: 2017-11-29Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-8541-1914

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