Inhibitory Effect of Chlorogenic Acid Analogues Comprising Pyridine and Pyrimidine on α-MSH-Stimulated Melanogenesis and Stability of Acyl Analogues in Methanol.

In continuation of studies for α-MSH stimulated melanogenesis inhibitors, we have evaluated the design, synthesis, and activity of a new series of chlorogenic acid (CGA) analogues comprising pyridine, pyrimidine, and diacyl derivatives. Among nineteen synthesized compounds, most of them (fifteen) exhibited better inhibitions of melanin formation in B16 melanoma cells. The results illustrated that a pyridine analogue 6f and a diacyl derivative 13a of CGA showed superior inhibition profiles (IC50: 2.5 ± 0.7 µM and 1.1 ± 0.1 µM, respectively) of α-MSH activities than positive controls, kojic acid and arbutin (IC50: 54 ± 1.5 µM and 380 ± 9.5 µM, respectively). The SAR studies showed that both -CF3 and -Cl groups exhibited better inhibition at the meta position on benzylamine than their ortho and para positions. In addition, the stability of diacyl analogues of CGA in methanol monitored by HPLC for 28 days indicated the steric bulkiness of acyl substituents as a key factor in their stability.

The effect of video-instructed versus audio-instructed dispatcher-assisted cardiopulmonary resuscitation on patient outcomes following out of hospital cardiac arrest in Seoul.

We aimed to investigate whether video-instructed dispatcher-assisted (DA)-cardiopulmonary resuscitation (CPR) improved neurologic recovery and survival to discharge compared to audio-instructed DA-CPR in adult out-of-hospital cardiac arrest (OHCA) patients in a metropolitan city with sufficient experience and facilities. A retrospective cohort study was conducted for adult bystander-witnessed OHCA patients administered DA-CPR due to presumed cardiac etiology between January 1, 2018 and October 31, 2019 in Seoul, Korea. The primary and secondary outcomes were the differences in favorable neurologic outcome and survival to discharge rates in adult OHCA patients in the two instruction groups. Binary logistic regression analysis was performed to identify the outcome predictors after DA-CPR. A total of 2109 adult OHCA patients with DA-CPR were enrolled. Numbers of elderly patients in audio instruction and video instruction were 1260 (73.2%) and 214 (55.3%), respectively. Elderly patients and those outside the home or medical facility were more likely to receive video instruction. Favorable neurologic outcome was observed more in patients who received video-instructed DA-CPR (n = 75, 19.4%) than in patients who received audio-instructed DA-CPR (n = 117, 6.8%). The survival to discharge rate was also higher in video-instructed DA-CPR (n = 105, 27.1%) than in audio-instructed DA-CPR (n = 211, 12.3%). Video-instructed DA-CPR was significantly associated with neurologic recovery (aOR = 2.11, 95% CI 1.48-3.01) and survival to discharge (aOR = 1.81, 95% CI 1.33-2.46) compared to audio-instructed DA-CPR in adult OHCA patients after adjusting for age, gender, underlying diseases and CPR location. Video-instructed DA-CPR was associated with favorable outcomes in adult patients with OHCA in a metropolitan city equipped with sufficient experience and facilities.

Efficacy of a new dispatcher-assisted cardiopulmonary resuscitation protocol with audio call-to-video call transition.

BACKGROUND: Video call based dispatcher-assisted cardiopulmonary resuscitation (V-DACPR) has been suggested to improve the quality of bystander cardiopulmonary resuscitation. In the current system, dispatchers must convert the audio calls to video calls to provide V-DACPR. We aimed to develop new audio call-to-video call transition protocols and test its efficacy and safety compared to conventional DACPR(C-DACPR). METHODS: This was a randomized controlled simulation trial that compared the quality of bystander chest compression that was performed under three different DACPR protocols: C-DACPR, V-DACPR with rapid transition, and V-DACPR with delayed transition. Adult volunteers excluding healthcare providers were recruited for the trial. The primary outcome of the study was the mean proportion of adequate hand positioning during chest compression. RESULTS: Simulation results of 131 volunteers were analyzed. The mean proportion of adequate hand positioning was highest in V-DACPR with rapid transition (V-DACPR with rapid transition vs. C-DACPR: 92.7% vs. 82.4%, p = 0.03). The mean chest compression depth was deeper in both V-DACPR groups than in the C-DACPR group (V-DACPR with rapid transition vs. C-DACPR: 40.7 mm vs. 35.9 mm, p = 0.01, V-DACPR with delayed transition vs. C- DACPR: 40.9 mm vs. 35.9 mm, p = 0.01). Improvement in the proportion of adequate hand positioning was observed in the V-DACPR groups (r = 0.25, p < 0.01 for rapid transition and r = 0.19, p < 0.01 for delayed transition). CONCLUSION: Participants in the V-DACPR groups performed higher quality chest compression with higher appropriate hand positioning and deeper compression depth compared to the C-DACPR group.

Arsenic trioxide induces depolymerization of microtubules in an acute promyelocytic leukemia cell line.

BACKGROUND: Arsenic trioxide (As(2)O(3)) is a well-known and effective treatment that can result in clinical remission for patients diagnosed with acute promyelocytic leukemia (APL). The biologic efficacy of As(2)O(3) in APL and solid tumor cells has been explained through its actions on anti-proliferation, anti-angiogenesis, and apoptotic signaling pathways. We theorize that As(2)O(3) activates a pathway that disrupts microtubule dynamics forming abnormal, nonfunctioning mitotic spindles, thus preventing cellular division. In this study, we investigated how As(2)O(3) induces apoptosis by causing microtubule dysfunction. METHODS: Cultured NB4 cells were treated with As(2)O(3), paclitaxel, and vincristine. Flow cytometric analysis was then performed. An MTT assay was used to determine drug-mediated cytotoxicity. For tubulin polymerization assay, each polymerized or soluble tubulin was measured. Microtubule assembly-disassembly was measured using a tubulin polymerization kit. Cellular microtubules were also observed with fluorescence microscopy. RESULTS: As(2)O(3) treatment disrupted tubulin assembly resulting in dysfunctional microtubules that cause death in APL cells. As(2)O(3) markedly enhanced the amount of depolymerized microtubules. The number of microtubule posttranslational modifications on an individual tubulin decreased with As(2)O(3) concentration. Immunocytochemistry revealed changes in the cellular microtubule network and formation of polymerized microtubules in As(2)O(3)-treated cells. CONCLUSION: The microtubules alterations found with As(2)O(3) treatment suggest that As(2)O(3) increases the depolymerized forms of tubulin in cells and that this is potentially due to arsenite's negative effects on spindle dynamics.

A novel synthetic compound PHID (8-Phenyl-6a, 7, 8, 9, 9a, 10-hexahydro-6H-isoindolo [5, 6-g] quinoxaline-7, 9-dione) protects SH-SY5Y cells against MPP(+)-induced cytotoxicity through inhibition of reactive oxygen species generation and JNK signaling.

1-Methyl-4-phenylpyridinium ion (MPP(+)), a neurotoxin selective to dopaminergic neurons and an inhibitor of mitochondrial complex I, has been widely used as an etiologic model of Parkinson's disease. In this study, we investigated the protective effects of a novel synthetic compound, 8-Phenyl-6a,7,8,9,9a,10-hexahydro-6H-isoindolo[5,6-g]quinoxaline-7,9-dione (PHID), on MPP(+)-induced cytotoxicity in SH-SY5Y cells. MPP(+) induced apoptosis characterized by generation of reactive oxygen species, caspase-3 activation, poly ADP ribose polymerase proteolysis and increase in Bax/Bcl-2 ratio were blocked by PHID in a dose-dependent fashion. Furthermore, MPP(+)-mediated activation of stress-activated protein kinase/c-Jun N-terminal kinase (JNK) was also inhibited by PHID in a dose-dependent manner. The results indicate that PHID protects against MPP(+)-induced apoptosis by blocking reactive oxygen species stimulation and JNK signaling pathways in SH-SY5Y cells, implicating the novel compound in the prevention of progressive neurodegenerative diseases such as Parkinson's disease.

Thiacremonone augments chemotherapeutic agent-induced growth inhibition in human colon cancer cells through inactivation of nuclear factor-{kappa}B.

Chemotherapeutic strategies commonly use multiple agents to overcome drug resistance and to lower drug toxicity. Activation of nuclear factor-kappaB (NF-kappaB) is implicated in drug resistance in cancer cells. Previously, we reported that thiacremonone, a novel sulfur compound isolated from garlic, inhibited NF-kappaB and cancer cell growth with IC(50) values about 100 microg/mL in colon cancer cells. In the present study, we tested whether thiacremonone could increase susceptibility of cancer cells to chemotherapeutics through inactivation of NF-kappaB. Colon cancer cells were cotreated with thiacremonone (50 microg/mL, half dose of IC(50)) and lower doses of each chemotherapeutic agent (half dose of IC(50)) for 24 hours. NF-kappaB activity was completely abrogated in cells treated with a combination of thiacremonone and docetaxel, whereas thiacremonone on its own did not alter NF-kappaB activity. This combined drug effect was also found with other anticancer drugs in colon cancer and in other cancer cells. In good correlation with inhibition of cell growth and NF-kappaB activity, the combination treatment also regulated NF-kappaB target genes. Oral treatment of mice with thiacremonone (1 mg/kg) by administering it in drinking water for 4 weeks significantly augmented docetaxel (1 mg/kg, i.p., four times)-induced decrease of tumor growth accompanied with regulation of NF-kappaB activity and NF-kappaB target genes. These results warrant carefully designed clinical studies investigating the combination of thiacremonone and commonly used chemotherapeutic agents for the treatment of human cancers.

Marinoscillum gen. nov., a member of the family 'Flexibacteraceae', with Marinoscillum pacificum sp. nov. from a marine sponge and Marinoscillum furvescens nom. rev., comb. nov.

A novel strain, designated MRN461(T), was isolated from a marine sponge in Micronesia. The 16S rRNA gene sequence of the isolate showed 95.6 % similarity with that of 'Microscilla furvescens' IFO (now NBRC) 15994. Phylogenetic analysis revealed that the isolate and 'Microscilla furvescens' IFO 15994 formed a distinct phyletic line within the family 'Flexibacteraceae'. Cells of strain MRN461(T) were Gram-negative, long filamentous rods, motile by gliding. Growth was observed at 15-40 degrees C (optimum, 33 degrees C), at pH 5.0-9.5 (optimum, pH 7.5) and in the presence of 0.5-7.0 % sea salts (optimum, 2.5 %). The major isoprenoid quinone was MK-7. The dominant fatty acids were summed feature 3 (comprising iso-C(15 : 0) 2-OH and/or C(16 : 1)omega7c; 34.8 %), C(16 : 1)omega5c (21.6 %) and iso-C(16 : 1) (19.8 %). The DNA G+C content was 41.5 mol%. On the basis of evidence from our polyphasic taxonomic study, strain MRN461(T) is classified within a novel genus and species in the family 'Flexibacteraceae', for which the name Marinoscillum pacificum gen. nov., sp. nov. is proposed. The type strain of Marinoscillum pacificum is strain MRN461(T) (=KCCM 42325(T) =JCM 14064(T)). The misclassified species '[Microscilla] furvescens' is transferred to the new genus as Marinoscillum furvescens (ex Lewin 1969) nom. rev., comb. nov., with LMG 13023(T) (=DSM 4134(T) =ATCC 23129(T) =NBRC 15994(T)) as the type strain.

Lacinutrix algicola sp. nov. and Lacinutrix mariniflava sp. nov., two novel marine alga-associated bacteria and emended description of the genus Lacinutrix.

Two heterotrophic, aerobic, yellow-pigmented, Gram-negative, non-gliding bacteria, designated AKS293(T) and AKS432(T), isolated from a red alga, were analysed using a polyphasic taxonomic approach. 16S rRNA gene sequence analysis revealed that the novel strains were affiliated to the genus Lacinutrix, a member of the family Flavobacteriaceae, showing sequence similarities of 96.1-96.4 % with respect to the type strain of Lacinutrix copepodicola. The two novel isolates shared 99.5 % 16S rRNA gene sequence similarity and 55.0 % DNA-DNA relatedness. They grew optimally at 17.5 degrees C and pH 6.5. The main cellular fatty acids of strain AKS293(T) were iso-C(15 : 0), iso-C(15 : 0) 3-OH and iso-C(16 : 0) 3-OH, while those of strain AKS432(T) were anteiso-C(15 : 0), iso-C(15 : 0), iso-C(15 : 1) and iso-C(15 : 0) 3-OH. In both cases, the major isoprenoid quinone was MK-6. The DNA G+C contents were 34.7 and 37.0 mol% for strains AKS293(T) and AKS432(T), respectively. The phylogenetic evidence, phenotypic data and DNA-DNA hybridization results support the differentiation of strains AKS293(T) and AKS432(T) from each other and from their closest relative, L. copepodicola DJ3(T). Therefore, strains AKS293(T) and AKS432(T) represent two novel species, for which the names Lacinutrix algicola sp. nov. and Lacinutrix mariniflava sp. nov. are proposed, respectively. The type strain of L. algicola sp. nov. is AKS293(T) (=KCCM 42313(T)=JCM 13825(T)) and the type strain of L. mariniflava sp. nov. is AKS432(T) (=KCCM 42306(T)=JCM 13824(T)). An emended description of the genus Lacinutrix is also proposed.

Improved thermostability and acetic acid tolerance of Escherichia coli via directed evolution of homoserine o-succinyltransferase.

In Escherichia coli, growth is limited at elevated temperatures mainly because of the instability of a single enzyme, homoserine o-succinyltransferase (MetA), the first enzyme in the methionine biosynthesis pathway. The metA gene from the thermophile Geobacillus kaustophilus cloned into the E. coli chromosome was found to enhance the growth of the host strain at elevated temperature (44 degrees C), thus confirming the limited growth of E. coli due to MetA instability. In order to improve E. coli growth at higher temperatures, we used random mutagenesis to obtain a thermostable MetA(E. coli) protein. Sequencing of the thermotolerant mutant showed five amino acid substitutions: S61T, E213V, I229T, N267D, and N271K. An E. coli strain with the mutated metA gene chromosomally inserted showed accelerated growth over a temperature range of 34 to 44 degrees C. We used the site-directed metA mutants to identify two amino acid residues responsible for the sensitivity of MetA(E. coli) to both heat and acids. Replacement of isoleucine 229 with threonine and asparagine 267 with aspartic acid stabilized the protein. The thermostable MetA(E. coli) enzymes showed less aggregation in vivo at higher temperature, as well as upon acetic acid treatment. The data presented here are the first to show improved E. coli growth at higher temperatures solely due to MetA stabilization and provide new knowledge for designing E. coli strains that grow at higher temperatures, thus reducing the cooling cost of bioprocesses.

Description of Croceitalea gen. nov. in the family Flavobacteriaceae with two species, Croceitalea eckloniae sp. nov. and Croceitalea dokdonensis sp. nov., isolated from the rhizosphere of the marine alga Ecklonia kurome.

Two novel bacterial strains, designated DOKDO 025(T) and DOKDO 023(T), were isolated on Dokdo Island, Korea, from the rhizosphere of the brown alga Ecklonia kurome. The strains were subjected to a polyphasic taxonomy study and were found to be Gram-negative, aerobic, rod-shaped, non-motile and orange-coloured. The isolates shared 96.3 % 16S rRNA gene sequence similarity. They showed 93.8-95.6 % 16S rRNA gene sequence similarity with respect to members of the genus Muricauda in the family Flavobacteriaceae, but formed a distinct phyletic line. Moreover, the cellular appendages reported for all Muricauda species were absent from strains DOKDO 025(T) and DOKDO 023(T). The predominant cellular fatty acids of strain DOKDO 025(T) were iso-C(15 : 0), iso-C(15 : 1) and one with an equivalent chain-length of 13.565 and those of strain DOKDO 023(T) were iso-C(15 : 0), iso-C(15 : 1) and iso-C(17 : 0) 3-OH. The DNA G+C content of strains DOKDO 025(T) and DOKDO 023(T) were 59.5 and 66.5 mol%, respectively, higher than any values found in recognized members of the family Flavobacteriaceae. The major respiratory quinone was MK-6. On the basis of evidence from the polyphasic study, strains DOKDO 025(T) and DOKDO 023(T) represent two novel species in a new genus, Croceitalea gen. nov., for which the names Croceitalea eckloniae sp. nov. (the type species) and Croceitalea dokdonensis sp. nov. are proposed. The type strain of Croceitalea eckloniae sp. nov. is DOKDO 025(T) (=KCCM 42309(T) =JCM 13827(T)) and that of Croceitalea dokdonensis sp. nov. is DOKDO 023(T) (=KCCM 42308(T) =JCM 13826(T)).

Sufflavibacter maritimus gen. nov., sp. nov., novel Flavobacteriaceae bacteria isolated from marine environments.

Four Gram-negative, chemoheterotrophic, nonmotile, yellow-colored strains were isolated from the East Sea or from deep-sea sediments of Nankai Trough by standard dilution plating. Characterization by polyphasic approaches indicated that the four strains are members of the same species. Phylogenetic analyses based on 16S rRNA gene sequences revealed that the strains formed a coherent and novel genus-level lineage within the family Flavobacteriaceae. The dominant cellular fatty acids were i-C15:0, 3-OH i-C17:0, and 2-OH i-C15:0 and/or C16:1 omega7c. Predominance of 2-OH i-C 15:0 and/or C16:1omega7c clearly differentiated the strains from closely related members. The DNA G+C contents ranged 35.1-36.2 mol%. It is proposed, from the polyphasic evidence, that the strains should be placed into a novel genus and species named Sufflavibacter maritimus gen. nov., sp. nov., with strain IMCC 1001T (=KCCM 42359T=NBRC 102039T) as the type strain.

Flagellimonas eckloniae gen. nov., sp. nov., a mesophilic marine bacterium of the family Flavobacteriaceae, isolated from the rhizosphere of Ecklonia kurome.

A marine bacterium, DOKDO 007(T), was isolated from the rhizosphere of the marine alga Ecklonia kurome collected from Dokdo Island, Korea, in October 2004. The strain produced orange-coloured colonies on marine agar 2216. 16S rRNA gene sequence analysis indicated that the novel isolate belonged to the family Flavobacteriaceae and showed relatively high sequence similarities with members of the genus Muricauda (92.0-94.0 %). Phylogenetic analysis based on nearly complete 16S rRNA gene sequences revealed that the novel isolate shared a lineage with members of the genera Muricauda and Costertonia. Cells were aerobic, Gram-negative rods producing non-diffusible carotenoid pigments. In contrast to all other members of the family Flavobacteriaceae, cells of DOKDO 007(T) were motile by means of a polar flagellum. Optimal growth occurred in the presence of 3.5-4 % (w/v) sea salts (corresponding to 2.7-3.1 % NaCl), at pH 8 and at temperatures of 26-29 degrees C. The novel strain required Ca(2+) ions in addition to NaCl for growth. The dominant fatty acids were iso-15 : 0, iso-15 : 1omega10c and 10-methyl-16 : 0. The major respiratory quinone was MK-6. The DNA G+C content was 56.3 mol%, an unusually high value for members of the family Flavobacteriaceae. On the basis of these polyphasic taxonomic data, strain DOKDO 007(T) should be classified as representing a new genus and novel species in the family Flavobacteriaceae, for which the name Flagellimonas eckloniae gen. nov., sp. nov. is proposed. The type strain is DOKDO 007(T) (=KCCM 42307(T)=JCM 13831(T)).

Shewanella spongiae sp. nov., isolated from a marine sponge.

A psychrophilic bacterium, designated strain HJ039(T), was isolated from a marine sponge collected in the East Sea of Korea (also known as the Sea of Japan). Cells were Gram-negative, motile and rod-shaped (1.8-3.54 microm x 0.27-0.73 microm). Growth was observed between 5 and 26 degrees C (optimum 15 degrees C), at pH 5.0-8.5 (optimum pH 6.0-6.5) and in the presence of 0-6.0 % NaCl (optimum 2.0 %). The 16S rRNA gene sequence of strain HJ039(T) showed high levels of similarity (93.7-95.4 %) with members of the genus Shewanella, especially with Shewanella gaetbuli TF-27(T) (95.2 %), Shewanella decolorationis S12(T) (94.9 %), Shewanella putrefaciens LMG 26268(T) (94.6 %), Shewanella hafniensis P010(T) (94.6 %), Shewanella algae ATCC 51192(T) (94.5 %) and Shewanella kaireitica c931(T) (94.5 %). However, phylogenetic analysis revealed that strain HJ039(T) shared a phyletic line with S. algae and Shewanella amazonensis. The major respiratory quinone was Q-8. The DNA G+C content was 52.8 mol%. The major fatty acids were i-13 : 0 (8.5 %), 15 : 0 (4.2 %), i-15 : 0 (23.2 %), i-15 : 1 (7.9 %), 16 : 0 (8.7 %), 16 : 1omega7 (21.0 %) and 17 : 1omega8 (6.4 %). From this polyphasic taxonomic evidence, strain HJ039(T) is considered to represent a novel species of the genus Shewanella, for which the name Shewanella spongiae sp. nov. is proposed. The type strain is HJ039(T) (=KCCM 42304(T)=JCM 13830(T)).

Synthesis and cytotoxic activities of 8-alkyl or 8-aryl-8,9-dihydro-7H-isoindolo[5,6-g]quinoxaline-7,9-diones.

A series of 8-alkyl- and 8-aryl-8,9-dihydro-7H-isoindolo[5,6- g]quinoxaline-7,9-diones were synthesized using sultine chemistry as a key step in good yield. These compounds were evaluated for their in vitro cytotoxicity against six human cancer cell lines (HCT15, SK-OV-3, A549, SNB19, MCF7 and MCF7/ADR).

Yeosuana aromativorans gen. nov., sp. nov., a mesophilic marine bacterium belonging to the family Flavobacteriaceae, isolated from estuarine sediment of the South Sea, Korea.

A marine bacterium, GW1-1T, capable of degrading benzo[a]pyrene (BaP), was isolated from estuarine sediments of the South Sea (the Korea Strait), Korea, after an enrichment culture maintained for 2 years in a medium supplemented with a mixture of BaP and pyrene. The strain formed yellowish-brown colonies on marine agar 2216. Cells were strictly aerobic, non-motile, Gram-negative rods and produced non-diffusible carotenoid pigments. Optimal growth occurred in the presence of 1 % (w/v) NaCl and at pH 7 and 33-36 degrees C. No growth occurred without supplementation with either CaCl2 or MgCl2, even in the presence of NaCl. Phylogenetic analysis based on the nearly complete sequence of the 16S rRNA gene revealed that the isolate formed a phyletic lineage with the genera Gelidibacter (93.9-94.7 % gene sequence similarity), Subsaximicrobium (93.3 %) and Subsaxibacter (93.9 %). The isolate also showed high sequence similarities to Gaetbulibacter saemankumensis (94.5 %), Algibacter lectus (94.2 %), members of the genus Bizionia (93.6-94.3 %) and Formosa algae (93.2 %), even though it belonged to a different phyletic line. The major respiratory quinones of the isolate were menaquinones MK-5 and MK-6. The DNA G+C content was 51.4 mol%. Dominant fatty acids were i-15 : 0, a-15 : 0, i-15 : 1omega10c and 16 : 1. On the basis of this polyphasic taxonomic evidence, strain GW1-1T is classified as a member of a novel genus and species in the family Flavobacteriaceae, for which the name Yeosuana aromativorans gen. nov., sp. nov. is proposed. The type strain of the type species is GW1-1T (=KCCM 42019T = JCM 12862T).

A theoretical study of thermal [1,3]-sigmatropic rearrangements of 3-trimethylsilyl-1-pyrazoline: concerted vs. stepwise mechanisms.

Possible reaction mechanisms of 1,3-silyl and 1,3-hydrogen thermal rearrangements of trimethylsilyl-1-pyrazoline and its model systems were theoretically explored using B3LYP, MP2, CR-CCSD(T), CASSCF(6,5), and MRMP2(6,5) theories. Nitrogen substitution at the center position of allylic moiety turned out to have a special stabilizing effect on diradical intermediates, allowing a stepwise pathway. This substitutional effect was attributed to the nitrogen lone pair electrons, which form strong pi-conjugations with diradicals. The second nitrogen substitution at the terminal allylic position selectively reduces the reaction barrier of antarafacial retention pathway, creating a competition between concerted and stepwise channels. The introduction of a five-membered ring imposes ring strain on the allylic moiety and increases steric hindrance, allowing no antarafacial channels. The combined effect of the nitrogen substitution and the five-membered ring further removes the possibility of concerted reaction pathways. Therefore 1,3-silyl migrations of 3-trimethylsilyl-1-pyrazoline were found to occur only through stepwise mechanisms, implying that the Woodward-Hoffmann rule is not operative. The 1,3-hydrogen migration also occur via a stepwise mechanism; however, it would not occur easily because its reaction barrier is much higher than that of 1,3-silyl migrations. Current study shows that a stepwise mechanism can be the dominant reaction pathway of some particular [1,3]-sigmatropic rearrangements.

Kordiimonas gwangyangensis gen. nov., sp. nov., a marine bacterium isolated from marine sediments that forms a distinct phyletic lineage (Kordiimonadales ord. nov.) in the 'Alphaproteobacteria'.

A marine bacterium, designated strain GW14-5(T), capable of degrading high-molecular-mass polycyclic aromatic hydrocarbons was isolated from the sediments of Gwangyang Bay, Republic of Korea, after enrichment culture for 2 years with a mixture of benzo[a]pyrene and pyrene. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the isolate forms a phyletic lineage that is distinct from the seven known orders within the 'Alphaproteobacteria'. 16S rRNA gene sequence similarity of strain GW14-5(T) to all recognized bacterial species was not greater than 92%. The dominant fatty acids of the isolate were i-17:1 (46.2%), i-15:0 (15.1%) and i-17:0 (12.6%). The major respiratory quinone was MK-5, and the DNA G+C content was 39.3 mol%. Cells of strain GW14-5(T) were Gram-negative, motile, catalase-positive, oxidase-positive and weakly halophilic. Glucose, N-acetylglucosamine and maltose were utilized as sole carbon sources. The strain was positive for beta-glucosidase activity. Optimal growth of strain GW14-5(T) was at pH 7.0 and 37-40 degrees C and required the presence of 2% (w/v) NaCl. On the basis of this evidence, strain GW14-5(T) represents a novel genus and species in the 'Alphaproteobacteria' for which the name Kordiimonas gwangyangensis gen. nov., sp. nov. is proposed. The novel order Kordiimonadales is proposed for the distinct phyletic line represented by the genus Kordiimonas. The type strain is GW14-5(T) (=KCCM 42021(T)=JCM 12864(T)).

Cycloaddition isomerizations of adsorbed 1,3-cyclohexadiene on Si(100)-2x1 surface: first neighbor interactions.

The initial and subsequent surface reaction mechanisms of 1,3-cyclohexadiene on the Si(100)-2x1 surface were theoretically explored, focusing on the possible first-neighbor interactions. Five different initial reaction channels leading to nine different surface products were identified, confirming previous experimental reports of inter-dimer structures. Among the nine identified products, five of these surface products are new species that have not previously been reported. Potential energy surface studies reveal that the net reaction barriers within a given channel are very small, indicating that the final product distributions within that channel are determined by thermodynamics. On the other hand, thermal isomerizations between different channels are not expected to occur easily. Therefore, the surface product distributions among the five different channels are more likely to be determined by kinetics. As a result, understanding the relationships among the available reaction channels both kinetically and thermodynamically is essential for properly interpreting the experimental results. The current study shows that the subsequent surface chemical reactions of unsaturated initial surface products are strongly coupled with the first-neighbor interactions.

Surface S(N)2 reaction by H2O on chlorinated Si(100)-2 x 1 surface.

The potential energy surfaces of one, two, and three water molecule sequential adsorptions on the symmetrically chlorinated Si(100)-2 x 1 surface were theoretically explored with SIMOMM:MP2/6-31G(d). The first water molecule adsorption to the surface dimer requires a higher reaction barrier than the subsequent second water molecule adsorption. The lone pair electrons of the incoming water molecule nucleophilically attack the surface Si atom to which the leaving Cl group is bonded, yielding an S(N)2 type transition state. At the same time, the Cl abstracts the H atom of the incoming water molecule, forming a unique four-membered ring conformation. The second water molecule adsorption to the same surface dimer requires a much lower reaction barrier, which is attributed to the surface cooperative effect by the surface hydroxyl group that can form a hydrogen bond with the incoming second water molecule. The third water molecule adsorption exhibits a higher reaction barrier than the first and the second water molecule adsorption channels but yields a thermodynamically more stable product. In general, it is expected that the surface Si-Cl bonds can be subjected to the substitution reactions by water molecules, yielding surface Si-OH bonds, which can be a good initial template for subsequent surface chemical modifications. However, oversaturations can be a competing side reaction under severe conditions, suggesting that the precise control of surface kinetic environments is necessary to tailor the final surface characteristics.

Comparative study of surface cycloadditions of ethylene and 2-butene on the Si(100)-2 x 1 surface.

Multireference wave functions were used to study the ethylene and 2-butene surface reactions on Si(100) in their lowest energy singlet states. In addition to the diradical pathway, a pi-complex pathway on the ethylene surface was found. The net barrier for the latter process is 4.5 kcal/mol higher than that for the former, making the pi-complex pathway kinetically less accessible. Therefore, although there is a competition between the two initial channels, the diradical path is slightly favored, and rotational isomerization is possible. However, since the initial potential energy surfaces of the two channels are different, depending on experimental conditions, the branching ratio between the two channels may change. Consequently, the combined effects that would favor one channel over the other may not derive directly from the initial reaction barrier. This provides an explanation of the experimental controversy. As a result, the final distributions of surface products may depend on the experimental kinetic environment, especially when the population change due to the rotational isomerization is expected to be very small. A significantly different reaction channel is found in the 2-butene surface reaction on Si(100), in which a methyl hydrogen easily transfers to the surface yielding a new type of surface product other than the expected [2 + 2] cycloaddition product, with a comparatively small activation barrier. Consequently, the overall surface reactions of ethylene and 2-butene may be quite different. Therefore, direct comparisons between ethylene and 2-butene experimental results would be very useful.