Benzophenone Moiety Research Articles

Intramolecular Photochemistry in β-Turned Dipeptide Bridged Molecules

Abstract Several benzophenone-β-turned dipeptide-alkyl chain molecules were prepared. In acetonitrile, intramolecular photochemical reaction of the synthetic molecules was investigated. The photoexcited benzophenone moiety abstracted selectively a hydrogen of the alkyl chain in the molecule. Such a site selectivity showed that the β-turned conformation might be rigid enough for the hydrogen abstraction in the excited state.

A mechanism for the electron beam lithography of solvent‐soluble photosensitive polyimides

AbstractSolvent‐soluble and intrinsically photosensitive polyimides were prepared, and their electron beam reaction was investigated. Negative tone patterns were formed by the electron beam irradiation of PI(BTDA/DEDPM) and PI(BEDA/DEDPM). The mechanism for the pattern formation of PI(BTDA/DEDPM) was determined from transient absorption measurements, changes in the molecular weights, and IR spectrum measurements to be crosslinking via hydrogen abstraction by the triplet excited state benzophenone moiety. For the case of PI(BEDA/DEDPM), the pattern was formed by insolubilization due to chemical change in the polymer. These reactions are found to be so inhomogeneous that insolubilization of the polymer occurs at an early stage of gelation.

Picosecond laser photolysis studies on the intramolecular photoreduction process of benzophenone by diphenylamine linked by spacers in acetonitrile solution

Photoinduced hydrogen abstraction (HA) processes of 1-(4-benzophenoxy)-3-[4-(phenyl-amino)phenoxy]propane (BP-O-(CH 2) 3-O-DPA) and 1-(4-benzophenoxy)-2-[4-(phenylamino)phenoxy]ethane (BP-O-(CH 2) 2-O-DPA) in acetonitrile solution were investigated by means of picosecond transient absorption spectroscopy. The stable ion pair (IP) formation followed by proton transfer (PT) resulting in the HA reaction was observed for the photoreduction of (BP-O-(CH 2) 2-O-DPA). On the other hand, in addition to inter-ionic PT in the stable IP, direct HA of excited triplet benzophenone ( 3BP*) moiety was observed for BP-O-(CH 2) 3-O-DPA. On the basis of the dependence of the apparent reaction mechanisms on the molecular conformation and by comparison with the intermolecular HA process, the role of the electron transfer or CT interaction in the HA process of 3BP* from the secondary amine was discussed.

Miscibility in polybenzimidazole/polyimide sulphone blends: a comparison of blends containing fluorinated and non-fluorinated polyimide sulphone

A comparison of miscibility is presented for blends containing a fluorinated and a non-fluorinated polyimide sulphone, of otherwise comparable structure, with polybenzimidazole [PBI, poly(2,2′-( m-phenylene)-5,5′-bibenzimidazole]. The miscibility behaviour was studied using Fourier transform infra-red ( FTi.r.) spectroscopy and thermal analysis. The NH and CO absorbance regions in the FTi.r. spectra show that the fluorine-containing group in the hexafluoroisopropylidene-containing polyimide (PI1) decreases the miscibility of this polyimide with PBI, whereas the carbonyl group in the benzophenone moiety in the second polyimide (PI2) enhances miscibility. In blends with low PBI content, PI2 forms uniform hydrogen bonds with PBI, and the strength of the hydrogen bonding is maximized at a blend composition of 50 50 wt% . FTi.r. spectra of the blends were also obtained as a function of temperature. Above the glass transition temperature the PBI/PI2 blends contain two phases: pure PI2 (present in small amounts) and the predominant miscible phase. Analysis of the carbonyl band could be related to glass transition behaviour in the blend. Finally, an enhanced degradation of PI2 in the presence of PBI was observed and is discussed.

Detecting precatalytic conformational changes in F1-ATPase with 4-benzoyl(benzoyl)-1-amidofluorescein, a novel fluorescent nucleotide site-specific photoaffinity label.

A novel photoaffinity label for studies with the F1-ATPase has been synthesized and found to be an effective reporter of subunit conformational changes that occur in this enzyme upon multiple nucleotide-binding site occupancy. The new probe, 4-benzoyl(benzoyl)-1-amidofluorescein (BzAF), which possesses structural similarity to purine nucleotides, exhibits bifunctional characteristics that enable it to bind covalently to the exchangeable nucleotide sites on beef heart F1 (via photoactivation of the benzophenone moiety) and, once covalently linked, emit environmentally sensitive fluorescence (via selective excitation of the fluorescein moiety). BzAF binds competitively with ATP in the absence of illumination, with a KI of 50 microM. Under actinic irradiation necessary for generating the covalently reacting diradical triplet state of benzophenone, BzAF behaves as a nucleotide site-directed photoaffinity label of exchangeable (catalytic) sites, and the resulting photoinhibition of ATPase activity displays pseudo first-order rate-saturation kinetics that support formation of a dissociable BzAF.F1 complex (k-1/k1 = 58 microM) prior to covalent binding. The BzAF-induced photoinactivation is protectable with native nucleotide ligand (e.g. MgADP, Kprotect = 0.4 mM). Added corroboration of a catalytic cooperativity mechanism for F1 was obtained by finding a molar stoichiometric ratio [( 3H]BzAF:F1) of 1 required for complete inhibition of ATPase activity. Steady-state fluorescence studies with a unisite-labeled BzAF.F1 complex (a catalytically inactive species on which at least one exchangeable nucleotide-binding site remains unoccupied) display a saturable fluorescence quenching of the bound fluorescein upon titration with MgADP, but no change with MgAMP. These data imply that the filling of more than one of the catalytic binding sites/mol of F1 with nucleotide signals a precatalytic conformational adjustment that is transmitted between catalytic sites and across the beta-alpha-beta domain of the enzyme's subunit structure.

Rotational dynamics of flexible‐chain molecules. 13C NMR relaxation study of hydrocarbon chains attached to a heavy anchor

Abstract13C spin‐lattice relaxation times (T1) were measured for resolved carbons in flexible‐chain molecules consisting of a hydrocarbon chain attached to benzophenone at the para position. Effective correlation times, teff, were determined from T1 data and used to discuss the motional features of these molecules as a function of chain length, chain unsaturation and type of linkage by which the chain is attached to the benzophenone moiety. Of particular interest is the finding that the overall motion and chain mobility are greatly affected by the introduction of an unsaturated bond in the chain, depending on its configuration and location in the hydrocarbon tail.

Substantivity of sunscreens—preparation and evaluation of some quaternary ammonium benzophenone derivatives

Synopsis In continuation of previous studies on keratin-substantive sunscreens, two series of quaternary ammonium compounds, derived from 2,4-dihydroxy and from 4-hydroxybenzophenone and containing O-alkyl and N-alkyl chains of different length were prepared and submitted to substantivity tests on wool, to microbiological tests on two bacterial and two fungal species, and to tests for allergenicity/irritation on human skin. All compounds were rapidly adsorbed by wool in aqueous solution: as expected, the maximum amounts adsorbed at equilibrium (S(max)), indicative of the skin substantivity, were greatest for the C12 N-alkyl derivatives, and showed a progressive decrease with increasing length of the N-alkyl substituent. No substantial substantivity differences were detected in four C12 quaternary derivatives, differing by the presence (or absence) of a 2-OH group in the benzophenone moiety and by the length of the O-alkyl (n= 2 or 3) side chain. When tested for antimicrobial activity, however, only the 4-hydroxybenzophenone C12 quaternary derivatives showed an order of activity comparable with that of two reference compounds. The conditions leading to a maximal antibacterial activity in the present compounds appeared to be the absence of the 2-OH group, and a shorter O-alkyl side chain. None of the new quaternary derivatives showed skin-irritant properties. The results of this investigation, while confirming the peak substantivity of C12 quaternary derivatives, indicate the possibility of dissociating, in a quaternary ammonium sunscreen, the skin substantivity from other unwanted side-effects, and offer some guidelines for the development of safer agents of this type.

Photo-chemical behaviour of poly(organophosphazenes): Part VI—Photo-stabilization of poly[bis(4-benzoylphenoxy)]phosphazene by energy transfer processes

Photo-degradation and photo-crosslinking of poly[bis(4-benzoylphenoxy)]-phosphazene, [NP-(-O-C 6H 4-CO-C 6H 5) 2] n′ originates from the first excited triplet state of the benzophenone moiety appended to the phosphazene polymer backbone. Both reactions can be inhibited by energy transfer processes to suitable energy acceptors. Evidence is given that both free naphthalene and naphthalene attached to the cyclophosphazene ring are able to quench the photo-reactivity of the benzophenone-supporting phosphazene polymer.

Polymeric Photoinitiators Containing Side‐chain Ketoaromatic Moieties for Fast Ultraviolet Initiated Polymerisation of Acrylic Monomers

AbstractThe synthesis of polymeric photoinitiators having side‐chain cyclohexylphenylketone as well as benzophenone moieties at different distances from the backbone is described. Study of the activity of the former systems, in the ultraviolet initiated polymerisation of acrylic monomers, indicates that a remarkable increase in the polymerisation rate is observed when the cyclohexylphenylketone chromophore is attached to the main chain through an ethereal linkage rather than an ester group. In the case of the latter systems, considerable improvement is observed in the photoinitiating activity with respect to the corresponding low molecular weight model compounds in the polymerisation of acrylic monomers. Moreover, in general the copolymers of benzophenone‐containing monomers show higher activity than the corresponding homopolymers. These results are discussed in terms of photoexcitation energy migration along the polymer chain, as well as of intramolecular hydrogen abstraction from both main and side chains. This last occurrence seems to be the main activation process, as suggested by a strict correlation between activity and hydrogen‐donating properties of the co‐units in the copolymers, Photophysical evidence supporting this point is also reported. Finally, the synthesis of polymeric photoinitiators, containing both benzophenone and tertiary amine groups in the same macromolecule, has been accomplished via copolymerisation of 4‐acryloxybenzophenone with 4‐(N,N‐dimethylamino)styrene. Preliminary data concerning photoinitiating activity of these last copolymers indicate that conformational mobility affects the formation capability of exciplexes and then the activity itself.

Identification of novel N-glucuronides in rat bile after administration of 450191-S, a 1H-1,2,4-triazolyl benzophenone derivative.

5-[2-Aminoacetamido)methyl]-1-[p-chloro-2-(o-chlorobenzoyl)phenyl] -N,N-dimethyl-1H-s-triazole-3-carboxamide hydrochloride dihydrate (450191-S) is a ring-opened derivative of 1,4-benzodiazepine, which is activated by desglycylation and subsequent cyclization. After 450191-S administration, rat bile contained three novel conjugates which released active metabolites possessing the 1,4-benzodiazepine structure through beta-glucuronidase hydrolysis. Since the released metabolites have no functional groups to conjugate with glucuronic acid, we speculated that the aglycone might be the ring-opened form of 1,4-benzodiazepine which spontaneously cyclizes after the release of glucuronic acid. This possibility was tested by chemically reducing the ketone group of the ring-opened 1,4-benzodiazepine glucuronate conjugates, which would prevent the spontaneous ring closure reaction after the release of the glucuronic acid moiety. The NaBH4 reduction of the ketone of the benzophenone moiety of the conjugates and subsequent treatment with beta-glucuronidase allowed identification of the reduced aglycones with authentic samples using gas chromatography-mass spectrometry.

The conformation of the C-terminal region of actin: A site-specific photocrosslinking study using benzophenone-4-maleimide

The site-specific photocrosslinker, benzophenone-4-maleimide, was used to label G-actin specifically at Cys-374, the penultimate residue from the C terminus. The resultant BP-G-actin was polymerized to form BP-F-actin, and both forms of actin were irradiated to activate the benzophenone moiety. We found that for BP-F-actin both intersubunit and intrasubunit photocrosslinks were formed. For BP-G-actin only a small amount of an internally photocrosslinked species was formed. These findings suggest that in the F-actin polymer, the C-terminal peptide is localized in a region between neighboring subunits. In contrast, in the G-actin monomer, the C-terminal peptide is relatively distant from the surface of the molecule.

Photochemical probes of the active site of myosin. Irradiation of trapped 3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate labels the 50-kilodalton heavy chain tryptic peptide.

3'-O-(4-Benzoyl)benzoyl-ATP (Bz2ATP), an analog of ATP containing a photoreactive benzophenone moiety, was used as a probe of the ATP binding site of myosin subfragment 1 (SF1). The inactivation of SF1 NH+4-EDTA ATPase by the bifunctional thiol crosslinking system cobalt(II)/cobalt(III) phenanthroline complexes was enhanced by Bz2ATP to the same degree as by ATP. This treatment resulted in the stable trapping of Bz2ATP at the active site in nearly stoichiometric amounts in a manner exactly analogous to ATP (Wells, J.A., and Yount, R.G. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 4966-4970). Irradiation of SF1 containing trapped [3H]Bz2ATP gave approximately 50% covalent incorporation of the trapped nucleotide into the enzyme. Analysis of photolabeled SF1 by gel electrophoresis showed that all of the [3H]Bz2ATP was attached to the 95-kDa heavy chain fragment. No label was found in the light chains. Similar analysis of the same protein after limited trypsin treatment demonstrated that approximately 75% of the [3H]Bz2ATP was bound to the central 50-kDa peptide and its 75-kDa precursor from the heavy chain. The N-terminal 25-kDa tryptic peptide, shown to be photolabeled by other ATP analogs (Szilagyi, L., Balint, M., Sreter, F.A., and Gergely, J. (1979) Biochem. Biophys. Res. Commun. 87, 936-945; Okamoto, Y., and Yount, R.G. (1983) Biophys. J. 41, 298a), was not labeled (less than 1%) by Bz2ATP. These results demonstrate that portions of the 50 kDa-peptide of the heavy chain are within 6-7 A of the ATP binding site on SF1 and possibly contribute to nucleotide binding.

Substituent Effects on the Mesophase Stability for Cholesteryl Benzoylbenzoates

Abstract The thermal properties of cholesteryl esters of substituted benzoylbenzoic acids were examined. The substituent effects on the thermal stability of the chloesteric phase of these esters are quite striking. For cholesteryl 4-(4′-substituted benzoyl)benzoates, the Ch-I transition temperatures are slightly influenced by an electronic effect of the substituents, because the bond direction of the substituents is tilted with respect to the long molecular axis. For cholesteryl 4-(3′-substituted benzoyl)benzoates and cholesteryl 3-(4′-substituted benzoyl)benzoates, the Ch-I transition temperatures are influenced by the polarizability anisotropy of the terminal phenyl ring, which probably gives rise to a change in the ratio of the number of more-linear isomers to the number of less-linear isomers. For cholesteryl 4-(2′-substituted benzoyl)benzoates, the substituents increase the angle between the two phenyl rings, i.e., the thickness of the benzophenone moiety, due to the repulsive interaction between the substituent(s) and ortho-hydrogens of the other phenyl ring, and therefore decrease the Ch-I transition temperature largely.

Chemical modification of polymers. XI. Photoreactive polymers from poly(vinylbenzyl chloride)

AbstractPhotocrosslinking has been observed in a number of polymers derived by chemical modification of poly(vinylbenzyl chloride). Included are polymers bearing pendant benzophenone, stilbazolium, fluorenone, carbazole, and sulfonylazido moieties. The synthesis and properties of these polymers are described.

The mechanism of energy transfer from poly-p-benzoylphenylacetimido-bovine serum albumin to small-molecule quenchers.

Abstract— Results of a quantitative photochemical study of poly‐p‐benzoylphenylacetimido‐bovine serum albumin in the presence of small‐molecule triplet quenchers are reported. The efficiency of quenching by organic salts containing low triplet energy chromophores is shown to be qualitatively dependent on their predicted association constants to the modified protein. In addition, quenching is inhibited by salts of organic acids which possess high binding affinities for the protein but do not contain chromophores of low triplet energy. Quantitative treatment of the quenching and inhibition data yields results which strongly support the operation of an ‘affinity controlled’ mechanism for triplet energy transfer from the benzophenone moieties of the modified‐bovine serum albumin to quenchers such as α‐naphthylacetate and trans‐cinnamate.