bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and screening of a small library of proline‐based biodendrimers for use as delivery agents
Authors: Sanclimens Glòria , Shen Hong , Giralt Ernest , Albericio Fernando , Saltzman Mark William , Royo Miriam
Published: May 2005

A small library of defined peptide dendrimers based on polyproline sequences was designed to demonstrate the feasibility of generating a new type of polymeric agent for therapeutic use. Structural modifications to dendrimer surfaces further enriched the diversity of the library. Data show that the prolinerich dendrimers can be internalized in human epithelial (HeLa) cells, demonstrating the importance of the dendrimeric motif. The promising results described herein suggest that controlled modification of the dendrimer surface should eventually yield proline dendrimers with therapeutic potential. © 2005 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 80: 800–814, 2005

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Fluorescence intensity decays of cyclohexane and methylcyclohexane with two‐photon excitation from a high repetition rate frequency‐doubled dye laser
Authors: Lakowicz Joseph R. , Gryczynski Ignacy
Published: May 2005

We observed fluorescence emission from cyclohexane (CH) and methylcyclohexane (MCH) using picosecond pulses at 298–300 nm from a frequency‐doubled cavity‐dumped R6G dye laser. The emission maxima for CH and MCH are 209 and 215 nm, respectively, which agree with previous studies using vacuum ultra‐violet (VUV) excitation near 150 nm. The fluorescence intensities depended quadratically on peak laser intensity indicating two‐photon excitation. The intensity decays resulting from two‐photon excitation were measured using frequency‐domain fluorometry and were found to be nearly singly exponential ranging from 0.59 to 0.80 ns. Two‐photon induced fluorescence of cyclic and linear alkanes may provide new intrinsic spectroscopic probes of biological molecules. © 1995 John Wiley & Sons, Inc.
The active site of bacteriorhodopsin. Two‐photon spectroscopic evidence for a positively charged chromophore binding site mediated by calcium
Authors: Stuart Jeffrey A. , Vought Bryan W. , Zhang Chian‐Fan , Birge Robert R.
Published: May 2005

The nature of the chromophore binding site of light‐adapted bacteriorhodopsin is analyzed by using all‐valence electron MNDO and MNDO‐PSDCI molecular orbital theory to interpret previously reported linear and nonlinear optical spectroscopic measurements. A total of 45 binding site models are investigated. The binding site is simulated by including the chromophore, the lysine residue (LYS216), the following nearby amino acids (ARG82, ASP85, ASP115, ASP212, THR90, TRP86, TRP138, TRP182, TYR57, TYR83, and TYR185) and zero, one, or two divalent cations. We conclude that the unique two‐photon properties of the chromophore are due in part to the electrostatic field associated with a Ca2+ ion near to the chromophore. Four amino acids and three water molecules contribute significantly to the assigned chromophore adjacent calcium binding site (ASP85, ASP212, TYR57 and TYR185), and two conformational minima are predicted. The higher energy conformation has the calcium ion stabilized primarily by ASP85 and the chromophore imine proton by ASP212. The lower energy conformation has the calcium ion stabilized primarily by ASP212 and the imine proton by ASP85. The latter configuration is more stable due to strong hydrogen bonding between TYR185 and ASP212 coupled with electrostatic stabilization of the divalent cation by TYR57. Although both tyrosine residues are predicted to exhibit some “unprotonated” character, models involving full deprotonation of either TYR57 or TYR185 do not fit the spectroscopic data. We conclude that the cation binding site identified in this study is the second high affinity binding site for calcium, and that the chromophore binding site is, to a first approximation, positively charged. The chromophore “1B” and “1A” states, despite extensive mixing, exhibit significantly different configurational character. The lowest‐lying “1B” state is dominated by single excitations (> 80% for all models studied) whereas the second‐excited “1A” state is dominated by double excitations (> 70% for all models studied with extensive participation by spin‐coupled triplet‐triplet excitations). © 1995 John Wiley & Sons, Inc.
Palaeodental studies using FT‐Raman spectroscopy
Authors: Edwards H. G. M. , Williams A. C. , Farwell D. W.
Published: May 2005

The FT‐Raman vibrational spectrum of a child's deciduous exfoliated tooth has been analysed and the spectral features assigned to hydroxyapatite and protein. Comparisons made with older teeth from a Romano‐British burial site (∼ 2k years) and fossilised animal teeth (∼ 1 M‐70 M years) indicate that the organic protein component has disappeared with interment, whereas spectroscopic features due to the inorganic phosphatic matrix are common to all samples, modern and ancient. The application of the technique to the non‐destructive analysis of archaeological samples and the recording of spectra from interred samples without detriment from fluorescent material is demonstrated. © 1995 John Wiley & Sons, Inc.
A comparative infrared spectroscopic study of human breast tumors and breast tumor cell xenografts
Authors: Fabian Heinz , Jackson Michael , Murphy Leigh , Watson Peter H. , Fichtner Iduna , Mantsch Henry H.
Published: May 2005

Fourier transform infrared spectroscopy has been applied to the study of human breast tumors, human breast tumor cell lines and xenografted human tumor cells. The results presented indicate that substantial differences exist on a macroscopic level between human tumors, xenografted tumors and human tumor cell lines, which are related to the presence of a significant connective tissue matrix in the tumors. On a macroscopic level tumor cell xenografts appear, in spectroscopic terms, to be relatively homogeneous with a relatively weak signature characteristic of connective tissue. Differences on a microscopic level between adjacent small (30 μm2) areas of the same xenografted tumor could be detected, which were due to local variations in collagen content. In addition to variations in collagen content, variation in the deposition of microscopic fat droplets throughout both human and xenografted tumors could be detected. These results indicate the care with which infrared spectroscopic studies of tissues must be carried out to avoid incorrect interpretation of results due to an incomplete understanding of tissue pathology. © 1995 John Wiley & Sons, Inc.
A comparative study of the binding effects of Mg2+, Ca2+, Sr2+, and Cd2+ on calmodulin by fourier‐transform infrared spectroscopy
Authors: Nara Masayuki , Tanokura Masaru , Yamamoto Tatsuyuki , Tasumi Mitsuo
Published: May 2005

Fourier‐transform infrared spectroscopy is applied to examine interactions between divalent metal ions (M2+) and the COO− groups in the M2+‐binding sites of calmodulin as well as effects of M2+ binding on the main chain conformation. Bands due to the symmetric and antisymmetric stretches of the COO− groups in the amino‐acid side chains give information on the coordination of the COO− groups to M2+, and the amide‐I' bands are useful for studying changes in the secondary structure of the protein main chain upon M2+ binding. Infrared deconvolved spectra as well as second‐derivative spectra are sensitive to structural differences among the M2+‐bound forms (M2+ = Mg2+, Ca2+, Sr2+, and Cd2+). Bands at about 1658, 1553, and 1424 cm−1 are characteristic of the Ca2+‐bound form, and are called, respectively, marker bands I, II, and III of the active‐type protein. The Sr2+‐ and Cd2+‐bound forms show deconvolved and second‐derivative spectra similar to those of the Ca2+‐bound form, whereas the Mg2+‐bound form gives second‐derivative and deconvolved spectra close to those of the inactive M2+‐free form. Broad parallelism is found to exist between the marker‐band intensities of the M2+‐bound forms and the abillities of M2+ to stimulate calmodulin‐dependent phosphodiesterase activity. Assignments of the marker bands are discussed. © 1995 John Wiley & Sons, Inc.
Fast photovoltage measurements in photosynthesis. I. Theory and data evaluation
Authors: Wulf Karsten , Trissl Hans‐Wilhelm
Published: May 2005

Fast photovoltage measurements are a valuable tool for the study of trapping of excitation energy, kinetics of charge separation, and relative distances of intermediary acceptors in the photosynthetic reaction center. Recent advances of both, the technique and the data analysis have not been described before. Here, in a first article of this sequence, we describe a theoretical model of the primary photosynthetic reactions and the computer analysis of transient photovoltage as well as of fluorescence data. The model assumes free energy migration between photosynthetic units and takes into account specific effects of high energy excitation like the acceleration of the trapping kinetics, the quenching of the excited state by oxidized reaction centers, and the nonlinear process of exciton‐exciton annihilation. Furthermore, the finite duration of the picosecond flashes is considered. The approximations involved in this model are discussed with respect to different functional antenna organizations. In a second article of this sequence we describe the experimental set‐up, calibration procedures and the application of the present theory to experimental data. © 1995 John Wiley & Sons, Inc.
Fast photovoltage measurements in photosynthesis. II. Experimental methods
Authors: Trissl Hans‐Wilhelm , Wulf Karsten
Published: May 2005

Fast photovoltage measurements in the pico‐ and nanosecond time range represent a valuable tool for the study of excitation energy trapping, kinetics of charge separation, and the location of intermediary acceptors in the photosynthetic reaction center. However, data recording and data analysis are complex. In a preceding article (Wulf and Trissl,Biospectroscopy,1(1995), pp. xx–xx) we have described the theoretical fundamentals of data analysis. Here we describe the experimental set‐up, calibration procedures, and strategies for the determination of the parameters involved. Limitations of the method will be discussed. © 1995 John Wiley & Sons, Inc.
Kinetics of decomposition of UV‐absorbing intermediate generated during electrochemical oxidation of 6‐mercaptopurine at stationary pyrolytic graphite electrode
Authors: Goyal R. N. , Verma Madhu Shri
Published: May 2005

Spectroscopic technique coupled with electrochemical oxidation has been used to study the redox‐mechanism of 6‐mercaptopurine. Electrochemical oxidation of 6‐mercaptopurine has been studied in the pH range 2.0–10.0 by linear and cyclic sweep voltammetry, coulometry and constant potential electrolysis. Spectroscopic technique has been used to monitor the clevage of the SS bond in the UV‐absorbing intermediate generated during electrooxidation. The decay has been observed in a pseudo first order reaction. The ultimate products of oxidation in controlled potential electrolysis have been found as 6‐mercaptopurine and purine‐6‐sulfinic acid. Tentative mechanisms for the formation of the products have also been suggested. It is concluded that spectroscopic studies coupled with electrochemical studies provide a uniquely invaluable insight into the redox mechanism of biologically significant molecules. © 1995 John Wiley & Sons, Inc.
FTIR spectra of deoxyoligonucleotide‐nogalamycin complexes
Authors: Missailidis S. , Hester R. E.
Published: May 2005

FTIR spectroscopy has been used to study the three self‐complementary oligonucleotides TGATCA, CGATCG, and TGTACA in the form of complexes with the anthracycline drug nogalamycin. These complexes were prepared under conditions that enable the bulky nogalamycin to intercalate into the double helixes of the oligonucleotide duplexes. Changes in the FTIR spectra on complexation are indicative of strong perturbation of the AT base pairs, in contrast with the effect of the structurally related drugs adriamycin and daunamycin, which show affinity for GC base pairs. These differences are attributed to binding interactions with the functional groups attached to the aglycone chromophore rather than to the specific site of drug intercalation in the double helix. © 1995 John Wiley & Sons, Inc.
Infrared spectroscopic data favor a global mode hydration in determining DNA conformation by water activity
Authors: Phole Walter , Bohl Martin
Published: May 2005

The conformational A–B transition of natural random‐sequence NaDNA can be evoked simply by increasing the water activity in the specimen. Infrared spectroscopic data create a basis for the idea that the relevant solvent action proceeds in a global sense comprising a collective influence of the water molecules belonging to DNA hydration shell rather than by directly bound water molecules. This conclusion is consistent with the results of Molecular Dynamics simulations applied to various DNA fragment‐water systems. © 1995 John Wiley & Sons, Inc.
Interaction between drugs and water‐soluble polymers: VIII. Binding position of naproxen to bovine serum albumin
Authors: Tanaka Masami , Asahi Yutaka , Masuda Seizo
Published: May 2005

The interaction between naproxen (NP) and bovine serum albumin (BSA) was investigated by equilibrium dialysis. Since the binding constant of NP to BSA was independent of ionic strength and decreased with increase of alkyl chain length of fatty acid added, the interaction between NP and BSA was considered to be due to hydrophobic mechanism. Chemical shifts in 1H‐NMR spectra of NP were independent of the concentration of NP and addition of BSA. Spin‐lattice relaxation time (T1) and spin‐spin relaxation time (T2) of respective protons of NP were independent of the concentration, but depended on the concentration of BSA added. The binding position of NP to BSA was considered to involve the hydrophobic aromatic moiety of NP from the ratio of spin‐spin relaxation rates (1/T2) of NP bound to BSA and free NP. © 1995 John Wiley & Sons, Inc.
Peroxidation of erythrocytes: FTIR spectroscopy studies of extracted lipids, isolated membranes, and intact cells
Authors: Moore David J. , Sills Richard H. , Mendelsohn Richard
Published: May 2005

Fourier transform infrared (FTIR) spectroscopy was used to directly monitor peroxidative damage to membrane phospholipid acyl chains in erythrocyte membranes. Samples were suspended in a mixed 2H2O/H2O buffer system, thereby producing a “spectral window” in the C‐H stretching region of the infrared spectrum. A decrease in the number of acyl chain CC bonds upon erythrocyte peroxidation was quantitated directly from the spectra of isolated membranes. Second‐derivative spectroscopy permitted the conformationally sensitive membrane acyl chain methylene stretching modes to be separated from the protein (mostly hemoglobin) vibrations that dominate the spectra of intact cells. The sensitivity of these modes in erythrocytes was then determined in a series of thermotropic experiments. The effect of peroxidation upon the membrane acyl chain conformational order was monitored in isolated membranes and intact cells. No change in conformational order was detected upon peroxidation in intact cell and ghost spectra. In contrast, experiments with pure unsaturated phospholipids demonstrated that decreasing the CC bond population results in increased conformational order. The finding of identical results for peroxidation versus control samples in isolated membranes (“ghosts”) validates the results observed for intact cells. FTIR technology permits the direct monitoring of conformational order in the acyl chains of intact cells. © 1995 John Wiley & Sons, Inc.
Infrared spectra of human central nervous system tissue: Diagnosis of alzheimer's disease by multivariate analyses
Authors: Choo L.‐P. , Mansfield J. R. , Pizzi N. , Somorjai R. L. , Jackson M. , Halliday W. C. , Mantsch H. H.
Published: May 2005

We present an infrared (IR) spectroscopic view of the pathological features of Alzheimer's disease (AD), along with a means of classifying the spectroscopic data nonsubjectively using several multivariate methods. The results demonstrate that IR spectroscopy can potentially be used in the diagnosis of AD from autopsy tissue. Although several spectral features that appear to be related to the disease process can be detected by a visual inspection of the IR spectra of AD grey matter, the appearance of these features was inconsistent. A more successful (consistent) diagnosis is achieved using multivariate analysis of the spectroscopic data. It is shown that correct classification of white and grey matter from brains identified by standard pathological methods as heavily, moderately, and minimally involved can be achieved with success rates of greater than 90% using appropriate methods. Classification of tissue as either control or AD was achieved with a success rate of 100%. © 1995 John Wiley & Sons, Inc.
Copper bilirubinate and black pigment gallstone
Authors: Li W.‐H. , Shen G.‐R. , Soloway R. D. , Yang Z.‐L. , Tong X.‐B. , Wu E. , Xu D.‐F. , Wu J.‐G. , Xu G.‐X.
Published: May 2005

A series of copper bilirubinate complexes (CuBR) was synthesized in solution and in solid state to mimic the black color of the black‐pigment gallstone and to explore the formation mechanism of the gallstonein vitro. The variation of the copper contents of these samples indicated that CuBR also exhibits nonstoichiometric characteristics from the FTIR study, i.e., both the so‐called acid and neutral copper complex moieties exist in CuBR. The NH groups in pyrrole and lactam groups of bilirubin (H2BR) are binding to the copper ions. An EPR study demonstrates the generation of free radicals and the variation of its electronic structure and conjugation system in the skeleton of H2BR molecule during complex formation. A polymer of CuBR may form through the reaction of H2BR with copper ions. © 1995 John Wiley & Sons, Inc.
Surface‐enhanced Raman spectroscopy of bilirubin‐metal ion complexes
Authors: He Jiping , Lu Xian Dan , Zhou Xingyao , Yu Nai‐teng , Chen Zhenhua
Published: May 2005

Surface‐Enhanced Raman Scattering (SERS) spectra of bilirubin–metal ion (Cu2+, Co2+, Zn2+, Cd2+) complexes (MBR) are reported. These spectra reveal significant differences between MBR and bilirubin (BR) itself. But SERS spectra of bilirubin–Cu2+, Co2+, Zn2+, Cd2+ complexes are similar to each other. The mole ratio of bilirubin‐metal in the complexes M2+ : BR = 1 : 1 was measured. Empirical assignments of the major SERS bands are given. The spectrum of CuBR in solution is consistent with a square planar structure. It should be noted, however, that H2O or COOH of another BR molecule occupy the positions above and below the plane in solutions of complexes of this type and forms CuO bond.

By comparing the SERS spectra of bilirubin‐copper (or zinc) and biliverdin‐copper (or zinc) complexes, the similar Raman frequencies and relative intensities were attributed to the oxidation of the bilirubin‐copper (or zinc) complex to the green biliverdin‐copper (Zn) complexes. It is shown that . © 1995 John Wiley & Sons, Inc.
DNA dynamics observed with long lifetime metal‐ligand complexes
Authors: Lakowicz Joseph R. , Malak Henryk , Gryczynski Ignacy , Castellano Felix N. , Meyer Gerald J.
Published: May 2005

Measurements of DNA dynamics are typically limited to the nanosecond timescale because of the nanosecond decay times of commonly used fluorophores such as ethidium bromide and acridine derivatives. We show that the time‐resolved anisotropy measurements can be extended to the submicrosecond timescale using metal‐ligand complexes. The ruthenium complex [Ru(2,2′,‐bipyridine)2(dipyrido[3,2‐a : 2′,3′‐c]phenazine)]2+, or [Ru(bpy)2(dppz)]2+, was found to display high anisotropy near 0.2, at −60°C in 100% glycerol, when excited in its long‐wavelength absorption bands. The decay time of [Ru(bpy)2(dppz)]2+ when bound to DNA is over 100 ns, allowing intensity to be measured to over 400 ns. Other Ru complexes display still longer lifetimes to 750 ns when bound to DNA. This class of fluorophores should enable measurement of DNA dynamics over a wide range of times (from 1 ns to several μs), which were previously inaccessible using time‐resolved fluorescence. © 1995 John Wiley & Sons, Inc.
Role of amino‐acid sidechains in electron‐transfer reactions in reaction center of rhodopseudomonas viridis as revealed by extended hückel molecular orbital calculations
Authors: Nakagawa Hiroyuki , Okada Takashi , Koyama Yasushi
Published: May 2005

The amino‐acid sequences of the L‐ and M‐subunits of the reaction centers (RC) from four purple photosynthetic bacteria were compared by the use of CLUSMOL/S (Clustering System for Molecules/Sequences), and conserved and character‐conserved amino acids were extracted. Extended Hückel molecular orbital (MO) calculations were made, based on the three‐dimensional structure of the Rhodopseudomonas viridis RC, for eleven composites of pigments, in which the sidechains (except for aliphatic sidechains) of the above amino acids within a distance of 6 Å from both of each pair of electron donor and acceptor were included. Calculations of the electronic coupling between each pair of donor and acceptor as well as evaluations of mixing of the lowest unoccupied molecular orbital (LUMO) of one chromophore with the orbitals of another chromophore and amino‐acid sidechains elucidated the roles of the sidechains in the electron transfer reactions: (1) L181‐Phe and M208‐Tyr function as a pair of bridges in the electronic coupling among pigments bacteriopheophytin in the M‐branch (HM), accessory bacteriochlorophyll in the M‐branch (BM), one of the special‐pair bacteriochlorophylls in the M‐branch (PM), one of the special‐pair bacteriochlorophylls in the L‐branch (PL), accessory bacteriochlorophyll in the L‐branch (BL), and bacteriopheophytin in the L‐branch (HL), and can affect the special‐pair bacteriochlorophylls (P) → HL electron transfer; (2) M250‐Trp plays a crucial role in the HL → primary quinone (QA) electron transfer, but L216‐Phe does not facilitate the HM → secondary quinone (QB) electron transfer; (3) the Fe2+ ion and the ligating histidines facilitate the QA → QB electron transfer; (4) L162‐Tyr plays a key role in the third heme in the cytochrome subunit (Heme) → P (PM plus PL) electron transfer. © 1995 John Wiley & Sons, Inc.
FTIR and EPR study of radicals of aromatic amino acids 4‐methylimidazole and phenol generated by UV irradiation
Authors: Berthomieu Catherine , Boussac Alain
Published: May 2005

The oxidized radicals of aromatic amino acids, 4‐methylimidazole and phenol were generated by UV irradiation at low temperature. The radicals were monitored by EPR spectroscopy. For the first time, infrared (IR) modes characteristic of the tyrosine, tryptophan, phenylalanine, and histidine radicals were obtained by FTIR difference spectroscopy between the ground state and the radical state. The effects of D‐ (on Tyr and phenol) or 15N‐ (on His) labeling on the IR modes of the radicals were studied, as were the influence of hydrogen bonding and of pH. These parameters were studied to model the possible radical structures and environments in proteins. The radicals obtained with tyrosine, phenol, and 4‐ethylphenol present six main IR modes: a combination mode at ∼ 2110–2106 cm−1; the v8b(CC) mode at 1550–1556 cm−1, the v7a(CO) and v19b(CC) modes both at 1515–1500 cm−1, which are distinctly affected by D‐labeling of the phenol ring; the 14(vCC + δCH) mode at 1290–1288 cm−1, which is strongly modified when the radical is hydrogen bonded; and the 9a(CC) mode at 1163–1159 cm−1. These IR modes partly confirm the assignments made by resonance Raman (RR) spectroscopy and should help to obtain precise structure and force field calculations for the radicals. The deprotonated 4‐methylimidazole radical (4‐MeIm·) is obtained at pH 12. It has characteristic IR modes at 1593 v(CC), 1425 δCH3, 1376 δCH3, 1315 cm−1, 1213 cm−1 and 1098 cm−1 δ(CH). The methyl modes seem strongly downshifted upon radical formation, while the ring modes appear less affected. In particular, the C4C5 double‐bond character is conserved. The protonated 4‐methylimidazole radical formed at pH ≤ 6 is characterized by signals at 1433 cm−1, 1380 cm−1, 1310 cm−1, 1227 cm−1, and 1172 cm−1. The histidine and tyrosine radicals present similar IR modes as the corresponding model of their sidechain. For all the amino acids, the vas(COO−) and vs(COO−) modes of the terminal carboxylate were respectively up‐ and downshifted by ∼ 20 cm−1 upon the radical formation. This effect suggests that, in a protein, the amide bond of the amino acid could also be influenced by the radical formation. © 1995 John Wiley & Sons, Inc.
Pressure‐induced secondary structure changes of ribonuclease A and ribonuclease S studied by FTIR spectroscopy
Authors: Takeda Naohiro , Kato Minoru , Taniguchi Yoshihiro
Published: May 2005

Fourier transform infrared (FTIR) spectroscopy combined with a resolution‐enhancement technique has been used to characterize pressure‐induced changes in the secondary structure of ribonuclease A (RNase A) and ribonuclease S (RNase S) in D2O solution at 30°C. According to the observed changes in the amide I' band, both RNase A and RNase S are reversibly unfolded by application of high pressure. The pressure‐unfolded state of the two proteins does not have any secondary structure elements characteristic of their native state, such as α‐helix, β‐sheet, and reverse turn. However, there is a slight difference in the structural features between pressure‐unfolded RNase A and RNase S, which is distinguished by the formation of nonnative turns only for RNase S. The dramatic structural transition of RNase A occurs over the pressure range between 570 and 1030 MPa. The pressure stability of RNase S is decreased by about 300 MPa compared with RNase A, despite little difference in the two native secondary structural features identified by FTIR spectroscopy. The structural features upon the pressure‐induced unfolding are additionally characterized by the interesting behavior of hydrogen‐deuterium exchange at high pressure. Most of the backbone amide protons protected at atmospheric pressure, which are involved in the α‐helices and β‐sheet of both RNase A and RNase S, are exchanged with solvent deuterons in the pressure range where the two secondary structure elements are virtually identified as intact. It is suggested that the solvent accessibility to the internal regions is strongly correlated to the pressure stability. © 1995 John Wiley & Sons, Inc.
Structure characterization of strontium (II) bilirubinate complexes
Authors: Liu Huizhou , Lu Kunquan , Soloway Roger D. , Yang Zhanlan , Zhao Yaqin , Wu Jinguang , Xu Guangxian
Published: May 2005

Calcium bilirubinate (CaBR) is the main component of pigment gallstones. At present no crystal structure of CaBR is available. Extended x‐ray absorption fine structure (EXAFS) is a powerful tool for local atomic structure determination, but it is difficult to measure the EXAFS spectra of calcium in compounds. Strontium bilirubinate (SrBR) was used instead of calcium, because of the similarity of IR spectra between CaBR and SrBR complexes. In this investigation a series of SrBR was synthesized. FTIR and EXAFS spectroscopic techniques were adapted to characterization. The results provide evidence of SrBR formation. It follows that the first shell about Sr (II) of the neutral BR compound consists of oxygen and nitrogen atoms with Sr‐O and Sr‐N distances of 2.61 Å and 2.69 Å, respectively. The coordination number of Sr is eight, consisting of four O atoms and four N atoms. It can lead to the unfolding of the coordination structure of CaBR. © 1995 John Wiley & Sons, Inc.
Determination of the hydrogen‐bonded structure of CGG trimers in chloroform solution by vibrational spectroscopy
Authors: Carmona P. , Molina M. , Lasagabaster A. , Escobar R.
Published: May 2005

Infrared and Raman spectra of 2′‐deoxy‐3′,5′‐bis (triisopropylsilyl) guanosine (G) and its 2 : 1 mixture with 2′‐deoxy‐3′,5′‐bis (triisopropylsilyl) cytidine (C) have been studied in chloroform solution. Strong interactions occur between CG base pair and a second G whose association constant was first determined. CGG trimer is stabilized by two hydrogen bonds between a G which is in a Watson‐Crick base pair and a second G. These interguanine hydrogen bonds involve the N(7) and O(6) guanine acceptors and N(1)H and N(2)H guanine donors. The 1570 cm−1 band of guanine is sensitive to hydrogen bonding at the N(3) position. Since this band is unchanged upon CGG formation, it is concluded that no binding at the guanine N(3) position occurs in the trimer. The pattern of hydrogen bonding in CGG trimer in chloroform solution here appears to correspond with patterns of hydrogen bonding in nucleic acid triplexes. These spectroscopic measurements constitute the first application of vibrational spectroscopy to the structural study of CGG trimer and self‐associated G in a nonaqueous solvent, and these nucleosides can be used as molecular models to know the hydrogen bonding in the hydrophobic interior of nucleic acid double and triple helices. © 1995 John Wiley & Sons, Inc.
Comparison of base inclinations for left‐handed DNA and RNA
Authors: Krittanai Chartchai , Kang Hunseung , Jin Xiaokui , Riazance‐Lawrence Jeannine H. , Curtis W. Johnson
Published: May 2005

The Z'‐form of poly(dG‐m5dC) · poly(dG‐m5dC) in 85% ethanol/MOPS and the Z‐form poly(rG‐rC) · poly(rG‐rC) in 4.8 M NaClO4, 20% ethanol are studied by flow linear dichroism. Simulataneous analysis of the isotropic absorption and linear dichroism data yields the angle of inclination of the base normal relative to the helix axis, and the orientation of the axis around which the bases incline. For the Z'‐form of poly(dG‐m5dC) · poly(dG‐m5dC) the inclination angles are 31.3° for guanine, and 27.9° for cytosine; for the Z‐form of poly(rG‐rC) · poly(rG‐rC) they are 25.0° for guanine, and 23.3° for cytosine. The inclination angles for the Z'‐form DNA are similar to those for the Z‐form, and the angles for Z‐form RNA are somewhat smaller. The axes of inclination for guanine and cytosine are similar in all three left‐handed forms. © 1995 John Wiley & Sons, Inc.
Raman depolarization ratios in RNA and DNA are sensitive for sugar‐base coupling
Authors: Terpstra P. A. , Otto C. , Segers‐Nolten G. M. J. , Kanger J. S. , Greve J.
Published: May 2005

Polarized and depolarized Raman spectra are obtained for a number of synthetic polynucleotides containing adenine, uracil, and thymine bases. The depolarization ratios are determined by two methods: (1) by dividing the ⟂‐spectrum by the ∥‐spectrum and (2) after curve fitting. Overlapping bands, isotope splitting, reorientational broadening, and noncoincidence splitting affect the magnitude of the depolarization ratios over the band‐width. For both Lorentz and Gauss curves these influences are simulated. A comparison of the Raman spectra of RNA and DNA molecules shows that the depolarization ratios for a number of similar base vibrations are different. The vibrational modes and the depolarization ratios of sugar vibrations are most sensitive to the structure of the polynucleotide. Base vibrations that have their potential energy distributed over base and sugar atoms also seem to be more sensitive to the structure. For instance the adenine vibrations at 1332 cm−1 and 1344 cm−1 in poly(dA), poly(dA) · poly(dT) and poly(dA‐dT) · poly(dA‐dT) have different depolarization ratios of, respectively, 0.36 and 0.28. This supports a previous assignment of the 1332 cm−1 band to a different sugar pucker (O4,‐endo) than the C2,‐endo corresponding with the 1344 cm−1 vibration. Assuming equal Raman scattering coefficients for this vibration, irrespective of the sugar pucker gives rise to the following ratio of the O4,‐endo/C2,‐endo in poly(dA) of 0.41, in poly(dA) · poly(dT) of 0.37, and in poly(dA‐dT) · poly(dA‐dT) of 0.41. © 1995 John Wiley & Sons, Inc.
Surface‐enhanced resonance raman spectroscopy of hypericin and emodin on silver colloids: SERRS and NIR FTSERS study
Authors: Jancura D. , Sánchez‐cortés S. , Kocisova E. , Tinti A. , Miskovsky P. , Bertoluzza A.
Published: May 2005

SERS, SERRS and NIR FTSERS of emodin and hypericin are reported for the first time on aqueous silver colloid. Intense SERRS spectra can be obtained when using excitation lines at 514 nm for emodin and 598 nm for hypericin. FTIR and NIR FTRaman spectra from these molecules and their model compounds, anthrone and bianthrone, were recorded to assist in the assignment of the SERS bands. From the analysis of the SERS spectra a different orientation for each molecule can be deduced. © 1995 John Wiley & Sons, Inc.
Comparative study of berenil– and pentamidine–poly‐nucleotide complexes using UV/VIS and FTIR spectroscopy
Authors: Schmitz Hans‐Uwe , Hübner Wigand
Published: May 2005

Fourier‐transform infrared (FTIR) spectroscopy was applied to investigate the conformational aspects of the synthetic polynucleotides poly d(AT), poly(dA)·poly(dT), poly(dA)·poly(dT)*poly(dT) upon binding of berenil and pentamidine. Measurements were performed in D2O to elucidate the hydrogen bonding system in the adducts. It could be demonstrated that intermolecular H‐bonds were formed between the minor groove binders berenil or pentamidine and the polynucleotides. The drug‐nucleotide interaction is followed by weak conformational distortions of the alternating polynucleotide poly d(AT), whereas such an effect is negligible in the poly(dA)·poly(dT) complexes. The binding of berenil or pentamidine into the minor groove of the triple‐stranded polynucleotide poly(dA)·poly(dT)*poly(dT) did not induce a dissociation of the third strand [poly(dT)] from the helical major groove. However, thermal denaturation profiles obtained by UV/VIS spectroscopy revealed a destabilization of the triplex due to the ligation of the drug molecules. This effect was accompanied by a “decreased binding density” in the triple helix compared with the poly(dA)·poly(dT) duplex. In contrast, both double‐helical polynucleotides were stabilized by the minor groove binders. The influence of pentamidine on the helical stability was smaller. Utilizing the attenuated total reflection (ATR) technique, conformational transitions of the double helices induced by variation of the water content in the films were monitored. The addition of berenil was followed by a suppression of these transitions, whereas for pentamidine no similar effects were observed. © 1995 John Wiley & Sons, Inc.
EXAFS and FTIR studies on the binding of deoxycholic acid with copper and zinc ions
Authors: Huang W. D. , Hu T. D. , Peng Q. , Soloway R. D. , Weng S. F. , Wu J. G.
Published: May 2005

Deoxycholic acid is an important physiological bile acid. The binding of bile salts with metal ions has received more attention due to its clinical significance. In this study, a series of copper and zinc deoxycholate complexes were synthesized. EXAFS and FTIR spectroscopic techniques were used for characterization. The results indicated that both the carboxyl and hydroxyl groups of deoxycholic acid are binding to the Cu (or Zn) ion to form a new complex. There are six oxygen atoms surrounding the metal ion with the average bond lengths of Cu‐O and Zn‐O are 1.95 and 2.06 Å respectively. © 1995 John Wiley & Sons, Inc.
Anharmonic force constants of helical molecules
Authors: Kutteh Ramzi , Van Zandt L. L.
Published: May 2005

Central to our anharmonic potential–effective charge method of computing relative Raman intensities of large helical molecules, such as DNA, are the anharmonic force constants of such molecules. We have thus been led to derive explicit expressions of them and to study their properties. These properties prove to be indispensable in carrying out the computational steps leading to the final Raman intensity expressions for helical molecules. A general expression of cubic force constants of a helical molecule is presented and its properties discussed. Explicit expressions are listed for the cases of stretch and anglebend contributions. Other uses of the anharmonic force constants are also discussed. © 1995 John Wiley & Sons, Inc.
Cover Picture: Quantum Dots Protected with Tiopronin: A New Fluorescence System for Cell‐Biology Studies (ChemBioChem 6/2005)
Authors: de la Fuente Jesus M. , Fandel Manuela , Berry Catherine C. , Riehle Mathis , Cronin Leroy , Aitchison Gregor , Curtis Adam S. G.
Published: May 2005

The cover picture shows the synthesis scheme for water‐soluble CdS nanocrystals that are protected with tiopronin, by using a straightforward and economical methodology. The chemical functionality of this capping agent provides a very high stability for the nanocrystals and has allowed us to functionalize quantum dots (QDs) with a HIV‐1 Tat protein‐derived peptide sequence. These nanocrystals are biocompatible with hTERT‐BJ1 human fibroblasts. Also shown is an overlay of the fluorescence (green; bottom left) and phase contrast images of hTERT‐BJ1 human fibroblasts incubated with CdS@tiopronin‐Tat. The functionalization of QDs with the translocation peptide permits them to penetrate the cell membrane and target the nucleus. Detailed information about the synthesis, functionalization and biocompatibility of these nanomaterials is reported by J. M. de la Fuente et al. on p. 989 ff.
Density Functional Study of Exchange Coupling Constants in Single‐Molecule Magnets: The Fe8 Complex
Authors: Ruiz Eliseo , Cano Joan , Alvarez Santiago
Published: May 2005

Theoretical methods based on density functional theory have been employed to analyze the exchange interactions in a Fe8 complex with single‐molecule magnet behavior. The four exchange coupling constants, calculated by using a hybrid functional, provide an accurate description of the experimental magnetic susceptibility and excitation energies. This complex has been also employed to check the accuracy of classical and quantum Monte Carlo methods to obtain macroscopic properties by comparison with the results obtained via exact diagonalization of the Hamiltonian matrix.
Plant Glycosyltransferases: Their Potential as Novel Biocatalysts
Authors: Lim Eng‐Kiat
Published: May 2005

The potential application of glycosyltransferases in glycoconjugate synthesis has attracted considerable interest from the biotechnology community in recent years. This concept article focuses on the current understanding of the chemistry of a family of plant enzymes capable of glycosylating small lipophilic molecules. These enzymes are discussed in terms of their regio‐ and enantioselective substrate recognition, sugar‐donor selectivity and their utility as biocatalysts in whole‐cell systems.
Cover Picture: Ligand Functionality as a Versatile Tool to Control the Assembly Behavior of Preformed Titania Nanocrystals (Chem. Eur. J. 12/2005)
Authors: Polleux Julien , Pinna Nicola , Antonietti Markus , Hess Christian , Wild Ute , Schlögl Robert , Niederberger Markus
Published: May 2005

Fussy functionalized crystal faces of titania nanocrystals, represented by surface‐functionalized octahedra in the cover picture, are found to spontaneously assemble into highly anisotropic nanostructures by means of oriented attachment in the [001] direction. M. Niederberger et al. describe the assembly behavior of preformed titania nanopowders in terms of the type of organic “assembler” molecule bound to the crystal surface in their article on page 3541 ff.
Atomic and Molecular Properties of Elements 112, 114, and 118
Authors: Nash Clinton S.
Published: May 2005

For Abstract see ChemInform Abstract in Full Text.
N4 Ring as a Square Planar Ligand in Novel MN4 Species
Authors: Cheng Li Ping , Li Qian Shu
Published: May 2005

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Predicted High‐Energy Molecules: Helical All‐Nitrogen and Helical Nitrogen‐Rich Ring Clusters
Authors: Wang Lijie , Mezey Paul G.
Published: May 2005

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Crystal Structure of Cs2Zn(NO2)4: Influence of Steric Crowding on Nitrite Coordination.
Authors: Oates Susan G. , Hitchman Michael A. , Skelton Brian W. , Stranger Robert , Stratemeier Horst , White Allan H.
Published: May 2005

For Abstract see ChemInform Abstract in Full Text.
Location and Orientation of Adsorbed Molecules in Zeolites from Solid‐State REAPDOR NMR
Authors: Holland Gregory P. , Alam Todd M.
Published: May 2005

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Crystal Structure and Magnetism of the Double Perovskite Sr3Fe2MoO9: A Neutron Diffraction Study.
Authors: Viola Maria C. , Alonso Jose A. , Pedregosa Jose C. , Carbonio Raul E.
Published: May 2005

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Phase Equilibrium of the In2O3—TiO2—MO (M: Ca, Sr) Systems and the Structure of In6Ti6CaO22.
Authors: Li Zhaofei , Sun Junliang , You Liping , Jiao Huan , Li Guobao , Jing Xiping , Liao Fuhui , Lin Jianhua
Published: May 2005

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Synthesis of Submicrometer‐Sized Electrochemically Active Lithium Cobalt Oxide via a Polymer Precursor.
Authors: Li Lan , Meyer Wolfgang H. , Wegner Gerhard , Wohlfahrt‐Mehrens Margret
Published: May 2005

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Mica Surfaces Stabilize Pentavalent Uranium.
Authors: Ilton Eugene S. , Haiduc Anca , Cahill Christopher L. , Felmy Andrew R.
Published: May 2005

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Na5(In4S) (InS4)3×6H2O, a Zeolite‐Like Structure with Unusual SIn4 Tetrahedra.
Authors: Zheng Nanfeng , Bu Xianhui , Feng Pingyun
Published: May 2005

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Synthesis of Elliptical Vanadoborates Housing Bimetallic Centers [Zn4(B2O4H2) (V10B28O74H8)]8‐ and [Mn4(C2O4) (V10B28O74H8)]10‐.
Authors: Wu Mingmei , Law Teresa S.‐C. , Sung Herman H.‐Y. , Cai Jiwen , Williams Ian D.
Published: May 2005

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Hydrothermal Synthesis of Crystalline Rectangular Titanoniobate Particles.
Authors: Li Bo , Hakuta Yukiya , Hayashi Hiromichi
Published: May 2005

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The First Sandwich‐Type Heteropolytungstates Consisting of Trivacant Gallium(III)‐Substituted Keggin Fragments.
Authors: Drews Daniel , Limanski Eva Melanie , Krebs Bernt
Published: May 2005

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Crystallographic Studies of a Molybdenum‐Rich Diarsenotungstate and Reaction of FeIII with Its Isomerically Pure α1‐ and α2‐Monolacunary Derivatives.
Authors: Mbomekalle Israel M. , Lu Yu Wei , Keita Bineta , Nadjo Louis , Neiwert Wade A. , Hardcastle Kenneth I. , Hill Craig L. , Anderson Travis M.
Published: May 2005

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Synthesis and Characterization of the Nitrogen‐Centered Trigonal Prismatic Clusters [W6NCl18]n‐ (n = 1—3).
Authors: Welch Eric J. , Yu Chun Liang , Crawford Nathan R. M. , Long Jeffrey R.
Published: May 2005

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Synthesis of a Misfit‐Layered Magnesium Manganese Hydroxide Oxide.
Authors: Xu Yaohua , Nakayama Noriaki , Fujiwara Keiko , Mizota Tadato , Goto Seishi
Published: May 2005

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Controlled Synthesis of Nanorods/Nanorings of a Novel Co—Cu Complex in Microemulsion at Room Temperature.
Authors: Sun Genban , Cao Minhua , Wang Yonghui , Hu Changwen , Ren Ling , Huang Kunli
Published: May 2005

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Practical P‐Chiral Phosphane Ligand for Rh‐Catalyzed Asymmetric Hydrogenation.
Authors: Liu Duan , Zhang Xumu
Published: May 2005

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PipPhos and MorfPhos: Privileged Monodentate Phosphoramidite Ligands for Rhodium‐Catalyzed Asymmetric Hydrogenation.
Authors: Bernsmann Heiko , van den Berg Michel , Hoen Rob , Minnaard Adriaan J. , Mehler Gerlinde , Reetz Manfred T. , de Vries Johannes , Feringa Ben L.
Published: May 2005

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Simple Derivatives of Natural Amino Acids as Chiral Ligands in the Catalytic Asymmetric Addition of Phenylacetylene to Aldehydes.
Authors: Han Zhi‐jian , Wang Rui , Zhou Yi‐feng , Liu Lei
Published: May 2005

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Asymmetric Hydrogenation of Chiral Vinyloxazaborolidines under Ambient Conditions.
Authors: Gamsey Soya , DeLaTorre Kelly , Singaram Bakthan
Published: May 2005

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Enantioselective Addition of Diethylzinc to Aldehydes in the Presence of Amino Thiocyanates Derived from L‐Prolinol.
Authors: Jin Myung‐Jong , Kim Young‐Mok
Published: May 2005

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Cyclization of 1‐{[(4‐Methyl‐4H‐1,2,4‐triazol‐3‐yl)sulfanyl]acetyl}thiosemicarbazides to 1,2,4‐Triazole and 1,3,4‐Thiadiazole Derivatives and Their Pharmacological Properties.
Authors: Maliszewska‐Guz Alicja , Wujec Monika , Pitucha Monika , Dobosz Maria , Chodkowska Anna , Jagiello‐Wojtowicz Ewa , Mazur Liliana , Koziol Anna E.
Published: May 2005

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A Short Asymmetric Total Synthesis of Chloramphenicol Using a Selectively Protected 1,2‐Diol.
Authors: Boruwa Joshodeep , Borah Jagat C. , Gogoi Siddhartha , Barua Nabin C.
Published: May 2005

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Microwave‐Assisted Preparation of Imidazolium‐Based Tetrachloroindate(III) and Their Application in the Tetrahydropyranylation of Alcohols.
Authors: Kim Yong Jin , Varma Rajender S.
Published: May 2005

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Pyridinium Chlorochromate Catalyzed Oxidation of Alcohols to Aldehydes and Ketones with Periodic Acid.
Authors: Hunsen Mo
Published: May 2005

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Rapid Mo(CO)6 Catalyzed One‐Pot Deoxygenation of Heterocyclic Halo‐Benzyl Alcohols with Lawesson′s Reagent.
Authors: Wu Xiongyu , Mahalingam A. K. , Alterman Mathias
Published: May 2005

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Direct Deoxygenation of Aryl Ketones Using Gallium(III) Chloride and Chlorodimethylsilane.
Authors: Choi Jaewoo , Kang Yonghan
Published: May 2005

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Use of CaH2 as a Reductive Hydride Source: Reduction of Ketones and Imines with CaH2/ZnX2 in the Presence of a Lewis Acid.
Authors: Aida Toshio , Kuboki Norikatsu , Kato Kenji , Uchikawa Wataru , Matsuno Chikashi , Okamoto Sentaro
Published: May 2005

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Halodephosphorylation of α,β‐Unsaturated Phosphonic Acid Monoesters.
Authors: Lahrache Hind , Robin Sylvie , Rousseau Gerard
Published: May 2005

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Copper(II) Tetrafluoroborate as a Novel and Highly Efficient Catalyst for Michael Addition of Mercaptans to α,β‐Unsaturated Carbonyl Compounds.
Authors: Garg Sanjeev K. , Kumar Raj , Chakraborti Asit K.
Published: May 2005

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An Efficient Synthesis of Sterically Hindered Arylboronic Acids.
Authors: Fang Hao , Kaur Gurpreet , Yan Jun , Wang Binghe
Published: May 2005

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Palladium‐Catalyzed Cross‐Coupling Reactions with Zinc, Boron, and Indium Exhibiting High Turnover Numbers (TONs): Use of Bidentate Phosphines and Other Critical Factors in Achieving High TONs.
Authors: Huang Zhihong , Qian Mingxing , Babinski David J. , Negishi Ei‐ichi
Published: May 2005

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An Unexpected Transformation of 1,2‐Dialkyldiaziridines into N‐{[Acetyl(alkyl)amino]methyl}‐N‐(alken‐1‐yl)acetamide under the Action of the Parent Ketene
Authors: Shevtsov Alexander V. , Petukhova Vera Yu. , Strelenko Yurii A. , Makhova Nina N.
Published: May 2005

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Carbolithiation of gem‐Aryl Disubstituted Methylenecyclopropanes.
Authors: Huang Jin‐Wen , Shi Min
Published: May 2005

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Enantioselective Copper‐Catalyzed Conjugate Addition to Trisubstituted Cyclohexenones: Construction of Stereogenic Quaternary Centers.
Authors: d'Augustin Magali , Palais Laeticia , Alexakis Alexandre
Published: May 2005

For Abstract see ChemInform Abstract in Full Text.