Best Articles

BEST ARTICLES JOURNAL OF THE CHINESE CHEMICAL SOCIETY

Each year, two or three best articles are chosen by the members of the Editorial Board of JCCS after receiving nominations from the Associate Editors and Review Board. All the awarded papers can be found in the available issues.

Volume: Please select the volume VOL.46 NO.5 (1999/10) VOL.47 NO.3 (2000/06) VOL.47 NO.5 (2000/10) VOL.48 NO.4 (2001/08) VOL.48 NO.6(A) (2001/12) VOL.49 NO.5 (2002/10) VOL.50 NO.3(B) (2003/06) VOL.50 NO.4 (2003/08) VOL.50 NO.5 (2003/10) VOL.51 NO.5(B) (2004/10) VOL.53 NO.1 (2006/02) VOL.53 NO.4 (2006/08) VOL.53 NO.6(2006/12) VOL.55 NO.1 (2008/02) VOL.55 NO.2 (2008/04) Page No: Please select the page No. Keyword:

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Preparation of Chiral Phosphorus(V) Reagents and Their Uses with Borane in the Enantioselective Reduction of Ketones
Guo-Hsian Chen, Jue-Liang Hsu, Wen-Bin Yang, Jim-Min Fang, Gene-Hsiang Lee, Yi-Hung Liu, Yu Wang
Chiral pentavalent phosphorus reagents 5-17 were prepared from POCI3 and ephedrine (or the related α-amino alcohols), followed by substitution with nucleophiles of phenylmagnesium bromide, alcohols, amines, diamines and triamines. The substitution reactions occurred in a stereospecific manner with retention of the configuration at the phosphorus center. The structures of these phosphorus (V) reagents were determined by spectral methods and verified by X-ray diffraction in several instances. These phosphorus (V) reagents were used with borane/dimethylsultide complex in the enantioselective reduction of aromatic, aliphatic and heterocyclic ketones. The phospborus (V) reagents likely functioned as Lewis bases to react with borane, forming in situ zwitterionic species as the chiral reducing agents. The reactions were generally car-tied out at 0℃ in teirabydrofuran solution with a molar ratio of ketone/borane/phosphoramidate=1:1:0.2 to afford secondary alcohols with modest enantioselectivity, up to 67% ee in the reduction of 4΄-methylace-tophenone.
VOL.46 NO.5 (1999/10)

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Structure-Reactivity Relationships as Probes for the Inhibition Mechanism of Cholesterol Esterase by Aryl Carbamates. Ⅰ. Steady-State Kinetics
Gialih Lin;Cheng-Yue Lai;Wei-Cheng Liao;Bing-Hong Kuo;Chun-Ping Lu
For substituted phenyl-N-butyl carbamates (1) and 4-nitrophenyl-N-substituted carbamates (2), linear relation ships between values of NH proton chemical shift (δ(subscript NH)), pKα, and logk(subscript [OH]) and Hammett substituent constant (δ) or Taft substituent constant (δ(superscript *)) are observed. Carbamates 1 and 2 are pseudo-substrate inhibitors of porcine pancreatic cholesterol esterase. Thus, the mechanism of the reaction necessitates that the inhibitor molecule and the enzyme form the enzyme-inhibitor tetrahedral species at the K(subscript i) step of the reaction and then form the carbamyl enzyme at the k(subscript c) step of the reaction. Linear relation ships between the logarithms of Ki and kc for cholesterol esterase by carbamates 1 and are observed, and the reaction constants (ρs) are -3.4 and -0.13, respectively. There fore, the above reaction forms the negative-charge tetrahedral species and follows the formation of the relatively neutral carbamyl enzymes. For the inhibition of cholesterol esterase by carba-mates 2 except 4-nitrophenyl-N-phenyl carbamate and 4-nitrophenyl-N-t-butyl carbamate, linear relation ships of-logK(subscript i) and logk(subscript c) with δ(superscript *) are observed and the ρ(superscript *) values are-0.50 and 1.03, respectively. Since the above reaction also forms the negative-charge tetrahedral intermediate, it is possible that the K(subscript i) step of this reaction is further divided into two steps. The first K(subscript i) step is the development of the positive-charge at the carbamate nitrogen from the protonation of the carbamate nitrogen. The second K(subscript i) step is the formation of the tetrahedral intermediate with the negative-charge at the carbonyl oxygen. From Arrhenius plots of a series of inhibition reactions by carbamates 1 and 2, the isokinetic and isoequilibrium temperatures are different from the reaction temperature (25℃). Therefore, the observed ρ and ρ(superscript *) values only depend upon the electronic effects of the substituents. Taken together, the cholesterol esterase inhibition mechanism by carbamates 1 and 2 is proposed.
VOL.47 NO.3 (2000/06)

Invited Paper	PDF file Download: 1009.pdf
Protein Folding and β-Sheet Proteins
Thallampuranam Krishnaswamy Suresh Kumar, Thirunavukkarasu Sivaraman, Dharmaraj Samuel, Sampath Srisailam, Gopal Ganesh, Hui-Chu Hsieh, Kuo-Wei Hung, Ho-Jen Peng, Meng-Chiao Ho, Alphonse Ignatius Arunkumar and Chin Yu
The aim of this comprehensive review is to critically evaluate the progress in research in the area of protein folding. In the first section, we discuss the various models proposed to explain the protein folding paradox. In the succeeding section of the review, a detailed account of the developments in our understanding of the folding pathways of -sheet proteins is provided.
VOL.47 NO.5 (2000/10)

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Tubular Morphology of Mesoporous Silica MCM-41
Hong-Ping Lin, Jyun-Hwei Hwang, Chung-Yuan Mou and Chih-Yuan Tang
We investigated detailed conditions for synthesizing the tubular form of MCM-41 mesoporous aluminosilicate. The method is the delayed neutralization method in which the rate of neutralization is one of the controlling factors. Rapid neutralization results in the particulate form while gradual neutralization leads to tubules. It is found that the tubule morphology has several sub-categories. There are thick-walled, think-walled hollow tubular MCM-4 1 and solid core tubules. There are void structures in the channel framework that makes the nanochannels to be effectively interconnected.
VOL.47 NO.5 (2000/10)

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The Host/Guest Type of Excited-State Proton Transfer; a General Review
Pi-Tai Chou
Con temporary progress regarding guest/host types of excited-state double pro ton transfer has been re-viewed, among which are the biprotonic transfer within doubly H-bonded host/guest complexes, the transfer through a sol vent bridge rel ay, the intramolecular double pro ton transfer and sol va tion dynamic coupled pro-ton transfer. Of particular emphases are the photophysical and photo chemical proper ties of excited-state dou-ble proton transfer (ESDPT) in 7-azaindole and its corresponding analogues. From the chemical aspect, two types of ESDPT reaction, namely the catalytic and non-catalytic types of ESDPT, have been classified and re-viewed sep a rately. For the case of static host/guest hydrogen-bonded complexes both hydrogen-bonding strength and con figuration (i.e. geometry) play key roles in ac counting for the re ac tion dynamics. In addition to the dynamical concern, ex cited-state thermo dynamics are of importance to fine-tune the pro ton transfer re-action in the non-catalytic host/guest type of ESDPT. The mechanisms of protic sol vent assisted ESDPT, de-pending on host molecules and pro ton-transfer models, have been re viewed where the plausible resolution is deduced. Particular attention has been given to the ex cited-state proton transfer dynamics in pure water, aiming atits future perspective in biological applications. Finally, the differentia tion in mechanism between sol-vent diffusive re organization and solvent relaxation to affect the host/guest ESPT dynamics is made and discussed in detail.
VOL.48 NO.4 (2001/08)

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Dynamics and Orientation Ordering of Water in Lyotropic Liquid Crystals Using 2H Double Quantum Filtered NMR Spectral Analysis
Chi-Yuan Cheng, Lian-Pin Hwang
The alignment of lyotropic liquid crystals in a magnetic field has been studied by line shape analysis of the T1 process and 2D 2H double quantum filtered (DQF) NMR to investigate water dynamics and orientational feature in Cetyltrimethylammonium bromide (CTAB)/Sodium Salicylate (NaSal)/D2O liquid crystals. The same system but in powder form was also examined. In the ordered liquid-crystalline phase, the single quantum line shapes showed splitting of doublets due to the residual quadrupolar interaction, while the double quantum spectra observed splitting patterns with damped oscillation. The modified cone model is invoked to describe the restricted motions of bound D2O molecules. Ten to thirteen bound water molecules are found to associate with each CTAB molecule and the correlation time of wobbling motion of the bound water is in the time scale of 10^(-8) s. At 10℃, the motional correlation times of water in the powder sample have the same magnitude as those in the oriented sample. This study shows that the analysis of DQF relaxation spectra provides a more detailed source of motional information than the normally used measurements.
VOL.48 NO.6(A) (2001/12)

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Molecular Rydberg States and Ionization Energy Studied by Two-Photon Resonant Ionization Spectroscopy
Yit-Tsong Chen
In this article, I will review the excited valence/Rydberg states and ionization energies of vinyl chloride, propyne, and allyl radical that we have examined recently in our laboratory by 2+1 resonance enhanced multiphoton ionization (REMPI) spectroscopy. In these studies, we have emphasized spectroscopic investigations from the first excited electronic states to the first ionization energies of the molecules and radicals of interest. In spectroscopic analysis, successful electronic identifications have been facilitated with theoretical (ab initio and density functional) calculations. In particular, we have applied calculated Franck-Condon factors to assist vibrational assignment for experimental vibronic spectra. The spectroscopic studies of these polyatomic excited valence/Rydberg states help us to illuminate the photodissociation pathways and to manifest the complicated chemical-reaction mechanisms due to the multi-dimensionality in polyatomic molecular potential energy surfaces.
VOL.49 NO.5 (2002/10)

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Single Molecule Spectroscopy
Tatiana Yu. Latychevskaia, Kuo Kan Liang*, Michitoshi Hayashi, Chung-Hung Chang, Alois Renn, Urs. P. Wild, Jui-Hung Hsu, Ta-Chau Chang, Sheng Hsien Lin
Single molecular experiments carried out in the group of Prof. Wild in ETH Zurich, as well as the experimental and theoretical studies of several research groups in Taiwan, have been summarized in this review. It is shown that with the contemporary technologies, single molecular experiments can be carried out under a broad range of physical conditions. These includes low and room temperatures; in vacuum, in solution, in the air, or with specific pressure applied on the sample; in applied direct-current or alternating-current electric fields; on molecules in solid matrices, in gel, or even functioning biomolecules in vitro. Theoretical efforts have been able to help identifying the interactions of single molecules with their surroundings that modulate their static or time-resolved spectroscopic properties. The joint experimental and theoretical effort to develop the research techniques in single molecular experiments is shown to be fruitful, and future works in this direction are important for many fields in chemistry, physics, and biology.
VOL.50 NO.3(B) (2003/06)

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Intramolecular [2+2] Photocycloaddition-Fragmentation: Facile Entry to a Novel Tricyclic 5-6-7 Ring System
Bor-Cherng Hong*, Shang-Hung Chen, Ellappan Sampath Kumar, Gene-Hsiang Lee and Kuan-Jiuh Lin
An expeditious route to a novel 5-6-7 tricyclic ring system is described. The chemistry capitalizes on an enantioselective glyoxylate-ene reaction, enzymatic resolution as well as a [2+2] photocycloaddition-fragmentation.
VOL.50 NO.4 (2003/08)

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Metal Binding and Selectivity in Zinc Proteins
Todor Dudev and Carmay Lim
Zinc is one of the most abundant metals in living organisms and is an essential co-factor of many metabolic enzymes and transcription factors. In this review, based on a recent body of theoretical and experimental results, the physical bases are delineated for the following aspects of zinc binding and selectivity in proteins: (1) What is the most thermodynamically preferable coordination geometry of a bidentate ligand (such as carboxylate) or Zn in Zn-binding sites? (2) What is the protonation state of the Cys side chain in Cys4 zincfinger cores? (3) How does a protein select Zn from the mixture of ions in the surrounding fluids? (4) What is the role of the second shell in metal binding and selectivity? The key results are summarized and the physical basis and/or implications of the findings are discussed.
VOL.50 NO.5 (2003/10)

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The Catalytic Copper Clusters of the Particulate Methane Monooxygenase from Methanotrophic Bacteria: Electron Paramagnetic Resonance Spectral Simulations
Shao-Ching Hung, Chang-Li Chen, Kelvin H.-C. Chen, Steve S.-F. Yu, Sunney I. Chan*
The particulate methane monooxygenase (pMMO) from Methylococcus capsulatus contains 14-15 reduced copper ions, and it has been proposed that these copper ions are arranged in the form of trinuclear clusters. Two of these clusters have been referred to as catalytic clusters (C-clusters) and have been implicated in dioxygen activation and alkane hydroxylation. The remaining copper ions appear to provide a “reservoir” of reducing equivalents to replenish the electrons at the C-clusters following dioxygen activation at the C-clusters during turnover. Accordingly, they are normally reduced and have been called electron-transfer clusters (E-clusters). For pMMO prepared in highly enriched membranes, or purified as the pMMO-detergent complex from these membranes, only the C-cluster copper ions are oxidized. Recently, the low temperature EPR spectrum of as-isolated pMMO was deconvoluted into a type 2 Cu(II) signal and a broad, but nearly isotropic EPR signal centered at g ~ 2.1. Earlier magnetization and magnetic susceptibility measurements have suggested that the latter EPR signal, which is not sensitive to microwave power saturation, might arise from a ferromagnetically exchange-coupled trinuclear Cu(II) cluster with J 20 cm-1 and D ≦0.05 cm-1. Toward confirming these results, several triangular model Cu(II) complexes, both antiferromagnetically and ferromagnetically coupled and with well-defined structural and ligand information, were reviewed to gain insights into magneto-structural correlations. Spectral simulations of the pMMO cluster EPR signals were then performed based on the structural and spectroscopic information provided by the ferromagnetic model complexes. We show that only Cu(II) ions with proper g-tensors and appropriate relative orientations between them can give rise to the unique EPR signal observed for the C-cluster(s) in pMMO. The putative C-cluster EPR signal observed for the as-isolated pMMO at 3 K was best fitted by a triad of ferromagnetically coupled Cu(II) ions with the following sets of g-values: (1.983, 2.030, 2.218), (1.983, 2.029, 2.218) and (2.000, 2.033, 2.207); and zero-field splitting parameters D = 0.017 ±0.002 cm-1 (175 ±25 Gauss) and E/D = 0.15. The fit was not sensitive to the value of J so long as the exchange interaction was much larger than the Zeeman interaction (J >> gβH).
VOL.51 NO.5(B) (2004/10)

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Feature Article: The Role of Seven-membered Ring in the Photoisomerization and Photodissociation of Small Aromatic Molecules
Chien-Ming Tseng, Yuri A. Dyakov, Cheng-Liang Huang, Yuan T. Lee, Sheng-Hsien Lin and Chi-Kung Ni*
Photoisomerization and photodissociation of toluene, xylene, 4-methyl-pyridine, and aniline under collision-free conditions are reviewed. For many years, it was thought that all the isomerization of aromatic molecules could be described in terms of ring permutation. One important characteristic of ring permutation is that the atoms belonging to the alkyl or amino groups attached to the aromatic ring are not involved in the exchange with the atoms within the aromatic ring. Only the relative positions of these alkyl or amino groups are changed. However, the observation of new dissociation products from toluene, xylene, 4-methyl-pyridine, and aniline suggests that a small fraction of these molecules undergo another kind of isomerization prior to dissociation. This isomerization involves the exchange between six-membered ring and seven-membered ring structures. It provides a new pathway for aromatic molecules to undergo totally different structural change. The significance of this isomerization is that the carbon atoms (or nitrogen atom) and hydrogen atoms belonging to the alkyl group (or amino group) attached to the aromatic ring are involved in an exchange with those atoms in the aromatic ring during the isomerization. The structural change and competition between isomerization and bond dissociation are discussed.
VOL.53 NO.1 (2006/02)

note	PDF file Download: 979.pdf
In situ Generated Palladium Nanoparticles for Catalytic Dehalogenation of Aryl Halides and Deboronation of Arylboronic acids¹
Rung-Yi Lai, Chuan-Lin Chen and Shiuh-Tzung Liu*
Palladium nanoparticles in situ generated from palladacyclic complexes efficiently catalyzed the deboronation of arylboronic acids and the dehalogenation as well as homo-coupling of aryl iodides in an alcohol medium under basic conditions. Isotope labeled studies indicated that the b-elimination of alcohols provided the hydrogen source for the reaction.
VOL.53 NO.4 (2006/08)

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Synthesis and Biolog Evaluation of 5'-Triazole Nucleosides
Wen-Shan Li
"The first series of 5'-triazole cytidines 1a-d and adenosines 2a-c was prepared and evaluated for inhibitory potency toward a-2,3-sialyltransferase. The synthesis of target compounds was achieved by converting the 5'-alcohol of protected nucleosides to th"
VOL.53 NO.6(2006/12)

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Ultrafast Spectrosco Studies on Thickness Dependence of Acoustic Phonon Modes in Silver Nanoprisms
Ying-Jen Shiu and Yit-Tsong Chena
"Time-resolved transient absorption technique is used to investigate the thickness dependence of acoustic phonon modes of silver nanoprisms with two thicknesses, 7.8
VOL.55 NO.1 (2008/02)

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Determination of Polybrominated Diphenyl Ethers in Coastal and River Sediments by Pressurized Liquid Extraction Coupled with Gas Chromatography-Mass Spectrometry
Yin-Ju Jhong and Wang-Hsien Ding*
This study presents a time- and solvent-saving method, pressurized liquid extraction (PLE), to extract polybrominated diphenyl ethers (PBDEs) in sediment samples. The effects of various operating parameters (i.e., extraction solution, temperature, pressure, static/dynamic extraction times) for the quantitative extraction of PBDEs by home-made PLE were systematically investigated and optimized. The analytes were then identified and quantitated by gas chromatography-mass spectrometry (GC-MS) in selected ion monitoring (SIM) mode. The 16 PBDE congeners (from tri- to deca-BDE) can be completely extracted by dichloromethane: n-hexane (3/2, v/v) at 100 °C and 100 atm combined with 15 min static and then 15 min dynamic extraction steps. Recovery of PBDEs in spiked sediment samples ranged from 52 to 104% with 2-16% RSD, except for BDE-206. Limits of quantitation (LOQ) were established between 4 and 400 pg/g (dry weight) in 10 g of sediment sample. The extraction efficiency of the PLE was also compared with the traditional Soxhlet extraction method. The total contents of PBDEs ranged from 8.0 to 37.9 ng/g (dry weight) in various river and coastal sediment samples in Taiwan. Deca-BDE (BDE-209) was the major PBDE detected in these sediment samples.
VOL.55 NO.2 (2008/04)