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  • 1. Liu, Junzhi
    et al.
    Osella, Silvio
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. Univ Mons, Belgium.
    Ma, Ji
    Berger, Reinhard
    Beljonne, David
    Schollmeyer, Dieter
    Feng, Xinliang
    Muellen, Klaus
    Fused Dibenzo[a,m]rubicene: A New Bowl-Shaped Subunit of C-70 Containing Two Pentagons2016Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 138, nr 27, s. 8364-8367Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Total synthetic approaches of fullerenes are the holy grail for organic chemistry. So far, the main attempts have focused on the synthesis of the buckmin-sterfullerene C-60. In contrast, access to subunits of the homologue C-70 remains challenging. Here, we demonstrate an efficient bottom-up strategy toward a novel bowl-shaped polycyclic aromatic hydrocarbons (PAH) C34 with two pentagons. This PAH represents a subunit for C-70 and of other higher fullerenes. The bowl-shaped structure was unambiguously determined by X-ray crystallography. A bowl-to-bowl inversion for a C-70 fragment in solution was investigated by dynamic NMR analysis, showing a bowl-to-bowl inversion energy (Delta G double dagger) of 16.7 kcal mol(-1), which is further corroborated by DFT calculations.

  • 2.
    Osella, Silvio
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Univ Warsaw, Ctr New Technol, Banacha 2C, PL-02097 Warsaw, Poland.
    Di Meo, Florent
    Limoges Univ, Fac Pharm, INSERM, UMR 1248, 2 Rue Docteur Marcland, F-87025 Limoges, France..
    Natarajan Arul, Murugan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi.
    Fabre, Gabin
    Limoges Univ, LCSN EA1069, Fac Pharm, 2 Rue Dr Marcland, F-87025 Limoges, France..
    Ameloot, Marcel
    Hasselt Univ, Biomed Res Inst, B-3590 Diepenbeek, Belgium..
    Trouillas, Patrick
    Limoges Univ, Fac Pharm, INSERM, UMR 1248, 2 Rue Docteur Marcland, F-87025 Limoges, France.;Palacky Univ, Ctr Adv Technol & Mat, Fac Sci, Tr 17 Listopadu 12, Olomouc 77146, Czech Republic..
    Knippenberg, Stefan
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Teoretisk kemi och biologi. Hasselt Univ, Biomed Res Inst, B-3590 Diepenbeek, Belgium..
    Combining (Non)linear Optical and Fluorescence Analysis of DiD To Enhance Lipid Phase Recognition2018Ingår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 14, nr 10, s. 5350-5359Artikel i tidskrift (Refereegranskat)
    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.

  • 3.
    Osella, Silvio
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Knippenberg, Stefan
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Triggering On/Off States of Photoswitchable Probes in Biological Environments2017Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 139, nr 12, s. 4418-4428Artikel i tidskrift (Refereegranskat)
    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.

  • 4.
    Osella, Silvio
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Minoia, Andrea
    Beljonne, David
    Combined Molecular Dynamics and Density Functional Theory Study of Azobenzene-Graphene Interfaces2016Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, nr 12, s. 6651-6658Artikel i tidskrift (Refereegranskat)
    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.

  • 5.
    Osella, Silvio
    et al.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Murugan, N. Arul
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Jena, Naresh K.
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Knippenberg, Stefan
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Investigation into Biological Environments through (Non)linear Optics: A Multiscale Study of Laurdan Derivatives2016Ingår i: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 12, nr 12, s. 6169-6181Artikel i tidskrift (Refereegranskat)
    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.

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