Probes photochemical

Structural and photochemical probes for electron transfer reactivity. J. F. Endicott, K. Kumar, T. Ramasami and F. P. Rotzinger, Prog. Inorg. Chem., 1983, 30,141-187 (185). 

Tsien, R. Y. Fluorescent and photochemical probes of dynamic biochemical signals inside living cells. In Fluorescent Chemosensors for Ion and Molecule Recognition. ACS symposium series 538, 1993. 

The quenching of benzophenone phosphorescence has been used by Mar and Winnik (1981) as a photochemical probe of hydrocarbon chains in solution. The bimolecular reaction for quenching the triplet state of 4-methoxy-carbonylbenzophenone [24] by 1-pentene occurs at rates which are below the diffusion limit by two to three orders of magnitude. Consequently, the intramolecular quenching reactions of to-alkenyl esters of benzophenone-4-carbo-xylic acid [25] occurs under conformational control. In [25] the point of... 

Structural and Photochemical Probes of Electron Transfer Reactivity.. 30 141... 

Dendrimers have precise compositional and constitutional aspects, but they can exhibit many possible conformations. Thus, they lack long-range order in the condensed phase, which makes it inappropriate to characterize the molecular-level structure of dendrimers by X-ray diffraction analysis. However, there have been many studies performed using indirect spectroscopic methods to characterize dendrimer structures, such as studies using photophysical and photochemical probes by UV-Vis and fluorescence spectroscopy, as well as studies using spin probes by EPR spectroscopy. 

Scheme 1 summarizes four different approaches used to characterize dendrimer structures by photophysical and photochemical probes 1. Non-covalent, inter-molecularly bound interior probes - to study the internal cavities and the encapsulation abilities of dendrimers. 2. Non-covalent, intermolecularly bound surface probes - to study surface characteristics of dendrimers. 3. Covalently linked probes on dendrimer surfaces - to study the molecular dynamics of dendrimers. 4. Covalently linked probes at the dendrimer central core - to study the site isolation of the core moiety and define the hydrodynamic volume of dendrimers by the concentric dendrimer shells. Critical literature in these four categories will be described using representative examples. 

Scheme 1 Four different approaches of photophysical and photochemical probes...

Structural and Photochemical Probes of Electron Transfer Reactivity. 

The potential use of 4-thiouracil as a photochemical probe in nucleic acid studies has been investigated in 5 -0-(2 -... 

Endicott, John F., Kumar, Krishan, Ramasami, T. and Rotzinger, Francois P., Structural and Photochemical Probes of Electron Transfer... 

It is more difficult to establish the preferred location and orientation of solute molecules within micelles. This information is required for the interpretation of kinetic results that may depend on these parameters (Section V). Often photochemical probes are used in attempts to analyze relevant data (Section VI). 

Fluorescent and Photochemical Probes of Dynamic Biochemical Signals inside Living Cells... 

Czamiecki, M. Breslow, R. Photochemical probes for model membrane structures. J. Am. Chem. Soc. 1979,101. 

Dolichols (98), a family of polyisoprenoid alcohols, have isolated from all eukaryotic cells or archaebacteria." They play a role in the co-translational modification of proteins and are known in iV-glycosylation in the form of dolichol phosphate. The synthesis of the photochemical probes 118 and 119 bearing a photoreactive group [3-(trifiuoromethyl)-3-aryldiazirine], analogues of dolichol and dolichol phosphate, is described in Scheme 5.19. The synthetic strategy involves the sequential alkylation of a monoterpenoid hydroxysulfonyl dianion with allyl chlorides, and MBH adduct 102 as a starting material. 

Additional physical evidence supporting the anticipated development of congestion as a function of generation is shown in the composite comparison in Fig. 42.13. Plots of intrinsic viscosity [tj], density z, surface area per Z group (Az), and refractive index n as a function of generation clearly show maxima or minima at generations = 3-5, paralleling computer-assisted molecular-simulation predictions [76] as well as extensive photochemical probe experiments reported by Turro et al. [90-93]. 

Some of the earliest reports describing supramolecular properties of PAMAM dendrimer interiors and surfaces were published by Turro et al. and have been reviewed extensively [123,124]. Utilizing both photophysical and photochemical probes many important supramolecular properties such as dendrimeric encapsulation, cooperative/noncooperative surface aggregations, and dendrimeric molecular morphogenesis were characterized and rationalized. 

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