The self-assembled monolayers (SAMs) of the new lipidic anchor molecule HC18 [Z 20-(Z-octadec-9-enyloxy)-3,6,9,12,15,18,22-heptaoxatetracont-31-ene-1-thiol], and mixed HC18/β-mercaptoethanol (βME) SAMs were studied by spectroscopic ellipsometry, contact angle measurements, reflection adsorption infrared spectroscopy (RAIRS), electrochemical impedance spectroscopy (EIS), and evaluated in tethered bilayer lipid membranes (tBLMs). Our data indicate that HC18, containing a double bond in the alkyl segments, forms highly disordered SAMs up to anchor/βME molar fraction ratios of 80/20 and result in tBLMs that exhibit higher lipid diffusion coefficients, relative to previous anchor compounds with saturated alkyl chains, as determined by fluorescence correlation spectroscopy. EIS data shows the HC18 tBLMs, completed by rapid solvent exchange (RSE) or vesicle fusion, form more easily than with saturated lipidic anchors, exhibit excellent electrical insulating properties indicating low defect densities, and readily incorporate the pore forming toxin, α-hemolysin. Neutron reflectivity measurements on HC18 tBLMs confirm the formation of complete tBLMs, even at low tether compositions and high ionic lipid compositions. Our data indicates HC18 results in tBLMs with improved physical properties for incorporation of integral membrane proteins (IMPs) and that 80% HC18 tBLMs appear to be optimal for practical applications such as biosensors where high electrical insulation and IMP/peptide reconstitution is imperative.

Time-resolved multi-pulse spectroscopic methods-pump-dump-probe (PDP) and femtosecond stimulated Raman spectroscopy-were used to investigate the excited state photodynamics of the carbonyl group containing carotenoid fucoxanthin (FX). PDP experiments show that S1 and ICT states in FX are strongly coupled and that the interstate equilibrium is rapidly (<5 ps) reestablished after one of the interacting states is deliberately depopulated. Femtosecond stimulated Raman scattering experiments indicate that S1 and ICT are vibrationally distinct species. Identification of the FSRS modes on the S1 and ICT potential energy surfaces allows us to predict a possible coupling channel for the state interaction.

Time-resolved multi-pulse methods were applied to investigate the excited state dynamics, the interstate couplings, and the excited state energy transfer pathways between the light-harvesting pigments in peridinin-chlorophyll a-protein (PCP). The utilized pump-dump-probe techniques are based on perturbation of the regular PCP energy transfer pathway. The PCP complexes were initially excited with an ultrashort pulse, resonant to the S→S transition of the carotenoid peridinin. A portion of the peridinin-based emissive intramolecular charge transfer (ICT) state was then depopulated by applying an ultrashort NIR pulse that perturbed the interaction between S and ICT states and the energy flow from the carotenoids to the chlorophylls. The presented data indicate that the peridinin S and ICT states are spectrally distinct and coexist in an excited state equilibrium in the PCP complex. Moreover, numeric analysis of the experimental data asserts ICT→Chl-a as the main energy transfer pathway in the photoexcited PCP systems.

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