UV and CD spectroscopy

Aggregates are microprecipitates of tens to thousands of polymer molecules which can be invisible to the naked eye or appear as a faint cloudiness in the solution. They form when a poor solvent such as methanol is added to a molecularly dispersed solution of the polymer in a good solvent, such as toluene or THF, or vice versa. Since aggregates are the first stage of a solid precipitate, they are also useful as model materials of the solid bulk state polymers and are amenable to study by many solution techniques such as solution-state UV and CD spectroscopy. Chiral molecules... 

Since the end of the seventies, interest in cyclotriveratrylene has moved towards the use of its cone shaped structure for applications in various fields, including investigations of the electronic transitions of the benzene chromophore via UV and CD spectroscopy, studies in the area of host-guest chemistry, synthesis of new types of liquid crystals, and searches for new three-dimensional organic charge-transfer materials. These works have been made possible because efficient synthetic... 

The aggregation of these oligomers has been studied by temperature-dependent UV and CD spectroscopy as well as by dynamic light scattering. ... 

Studies continue of the intercalation of DNA with various pyridyl platinum(ll) complexes. UV and CD spectroscopy, used with melting point and viscosity methods, showed the furthest extending aromatic planes of... 

Bioconjugates of 6A,6B-dideoxy-6A,6B-di[(A-salicylidene)amino]-p-CD, synthesised and characterised by NMR, UV and CD spectroscopy, were used to prepare a manganese salen-type Kgand with superoxide dismutase activity. 

Key words DNA-surfactant complexes - toroidal conformation - sedimentation - UV and CD spectroscopy - scanning tunneling and atomic force microscopy... 

Similarly, this amphiphilic polymer micelle was also used to dismpt the complex between cytochrome c (Cc) and cytochrome c peroxidase (CcP Sandanaraj, Bayraktar et al. 2007). In this case, we found that the polymer modulates the redox properties of the protein upon binding. The polymer binding exposes the heme cofactor of the protein, which is buried in the protein and alters the coordination environment of the metal. The exposure of heme was confirmed by UV-vis, CD spectroscopy, fluorescence spectroscopy, and electrochemical kinetic smdies. The rate constant of electron transfer (fc°) increased by 3 orders of magnimde for the protein-polymer complex compared to protein alone. To establish that the polymer micelle is capable of disrupting the Cc-CcP complex, the polymer micelle was added to the preformed Cc-CcP complex. The observed for this complex was the same as that of the Cc-polymer complex, which confirms that the polymer micelle is indeed capable of disrupting the Cc-CcP complex. 

Free ligands have been studied in order to obtain an insight into their structure, both in solution and in the solid state, and for comparison with their metal complexes. H NMR spectroscopy has been used to investigate the keto-enol equilibrium and the nature of the hydrogen bonds. In the case of optically active Schiff bases UV and CD spectra provided information about structure in solution. The Schiff bases that have been most widely examined are derivatives of acetylacetone, salicyl-aldehyde and hydroxymethylenecamphor, whose prototypes with en are shown in Figure 13. 

One approach towards such a system was accomplished by the synthesis and examination of (S)-l,T-binaphthyl-2,2 -diyl bis[4-(l,l-dicyano-l,8a-dihydro-(8aS)-azu-len-2-yl)]-benzoate (30a), monitoring its photochromic behavior by UV/Vis and CD spectroscopy. After irradiation of a solution of 30a in acetonitrile for 15.5 min, fundamentally altering its spectral properties, subsequent thermal relaxation in the dark for 12h resulted in complete restoration of the UV/Vis and CD spectra. This is a first step towards a powerful DHA/VHF-based information storage system controlled by asymmetric induction. Further investigations are underway. 

Monolayer FOms Transferred to Solid Substrates. Historically, the spectroscopic investigation of monolayer physical structure has been performed on films transferred to solid substrates, usually through conventional L-B techniques. A wide variety of methods may then be employed in the study of these films. For example, ultraviolet, circular dichroism, and IR spectroscopy, as well as electron microscopy have been performed on monolayers transferred to quartz (for UV and CD), Ge (for IR), and mica (for EM). While much useful information has been obtained in the study of transferred monolayers, there is always a concern about whether the actual physical process of transfer from a gas-liquid to a gas-solid interface induces a change in the structure of the molecule. 

Competition experiments showed that C6() could be displaced from the nanotube by selected ion pairs, resulting in the formation of mixed Cgo-ion pair complexes [32], The addition of 1 equiv. of XIV Cl to a 10-mM solution of Cgo-encapsulated 2 resulted in the precipitation of solid C60 and a colour change of the supernatant from brown to light orange (Fig. 41). The displacement of C6o from the nanotubular cavity was confirmed using UV-vis and CD spectroscopy the intensity of... 

Infra-red (IR) spectroscopy functions to probe vibrational transitions (2000-50 000 nm 5000-200 cm i.e. wave number - typical IR spectroscopy units) in the singlet ground electronic state of molecules. The absorption principles of IR spectroscopy are identical to those of UV-visible and CD spectroscopy. Hence the Beer-Lambert law (Equation (4.3)) applies. Moreover, absorption band intensities are determined by the transition dipole moment and there are extensive perturbation and coupling effects. Overall though, values of molar extinction coefficients for vibrational transitions, are up to 10 times lower in magnitude... 

Fluorescence spectroscopy in combination with circular dichroism (CD), optical rotatory dispersion. X-ray crystallography, UV and NMR spectroscopy of the main chain is a powerful probe for identifying helical conformation, uniformity, and rigidity in polymers. In recent years, these techniques have been applied extensively to investigate the structures of polysilanes in both the solid state and in solution and it is now clear that after electronic structure main chain helicity is the principal determinant of the properties of polysilanes. In... 

The bouquet (91), incorporated into a phospholipid membrane of liposomes, increases the permeability of the membrane to Na" and Li. The ion transfer proceeds via a cation-cation antiport mechanism which has been established by Na and Li NMR spectroscopy <92AG(E)1637>. The incorporation of the bouquet molecule into several vesicular systems has been monitored by numerous techniques (UV, NMR, and CD spectroscopies, differential scanning calorimetry). It was concluded that different modes of incorporation take place and that several orientations of the bouquet coexist in the membranes <93JCS(P2)ioii>. 

So far, detailed conformational studies on PMDS itself have been performed by using UV-VIS and CD spectroscopies. Accordingly, on the basis... 

An unsymmetrical L-proline-functionalized metallo-organic triangle incorporating cobalt(II) acts as a size-, diastereo-, and enantio-selective catalyst for aldols the reactions have been followed by MS, NMR, UV-vis, and CD spectroscopy. ... 

The interaction between p-nitrophenol and methyl-3-CD in solution was studied by UV and PMR spectroscopies. It was concluded that... 

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