Biomedical subjects

Yin Li

Publications and source records attributed to Yin Li.

At least 55 records · Page 3Linked to original sources

PubMed2005

Heterologous leaky production of transglutaminase in Lactococcus lactis significantly enhances the growth performance of the host.

This study describes a novel strategy to improve the growth performance of Lactococcus lactis by heterologous production of food-grade transglutaminase. The mtg gene from Streptoverticillium mobaraense that encodes the transglutaminase mature protein was cloned into a nisin-inducible expression vector and transformed into L. lactis subsp. cremoris NZ9000. The leaky expression of the mtg gene from the nisA promoter resulted in ammonia formation and carbon flux redistribution at the pyruvate branch. As a consequence, medium acidification was lessened and energy utilization was improved. This led to significantly higher biomass production under aerobic conditions and particularly under non-pH-controlled conditions (up to a 12-fold increase). The results presented here provide a novel way to enhance the growth yield of L. lactis, which is an important step for the purposes of producing proteins of commercial interest using L. lactis as a host.

Base Sequence↗

PubMed2005

Selective induction of apoptosis in mutant p53 premalignant and malignant cancer cells by PRIMA-1 through the c-Jun-NH2-kinase pathway.

PRIMA-1 (p53 reactivation and induction of massive apoptosis) is a chemical compound that was originally identified as a selective mutant p53-dependent growth suppressor by screening a library of low-molecular-weight compounds. However, its mechanism of action is unknown. In this study, we examined toxicity of PRIMA-1 to three premalignant human colorectal adenoma cell lines (RG/C2, BR/C1, and AA/C1) and four colorectal carcinoma cell lines (DLD-1, SW480, LOVO, and HCT116) and its mechanism of action. It selectively induced apoptosis only in the mutant p53 premalignant and malignant colon cell lines, but was not toxic to the wild-type p53 premalignant and malignant colon cell lines. Using stable transfectants of temperature-sensitive p53 mutant Ala(143) in null p53 H1299 lung cancer cells, we found that PRIMA-1 induced significantly more apoptosis in cells with mutant p53 conformation (37 degrees C) than the wild-type p53 conformation (32.5 degrees C). Cell cycle analysis indicated that its inhibition of cell growth was correlated with induction of G(2) arrest. Western blot analysis showed PRIMA-1 increased p21 and GADD45 expression selectively in the mutant p53 cells. However, Fas, Bcl-2 family proteins, and caspases were not involved in PRIMA-1-induced cell death. The c-Jun-NH(2)-kinase (JNK) inhibitor SP 600125, but not p38 mitogen-activated protein kinase inhibitor SB 203580 or extracellular signal-regulated kinase inhibitor PD 98059, blocked PRIMA-1-induced apoptosis. Transfection with a dominant-negative phosphorylation mutant JNK, but not a dominant-negative p38 or wild-type JNK, inhibited PRIMA-1-induced cell death, suggesting that the JNK pathway plays an important role in PRIMA-1-induced apoptosis. PRIMA-1 is a highly selective small molecule toxic to p53 mutant cells and may serve as a prototype for the development of new p53-targeting agents for therapy of premalignant and malignant cells.

Apoptosis↗

PubMed2005

[Application of a metabolic-pathway-analysis based breeding strategy enhances the production of pyruvate by Torulopsis glabrata].

To further enhance the pyruvate productivity by multi-vitamin auxotrophic yeast Torulopsis glabrata, a breeding strategy aiming at decreasing the activity of pyruvate decarboxylase but increasing the activity of acetyl-CoA synthetase was developed based on analysis of pyruvate-related metabolic pathways. Nitrosoguanidine mutagenized cells of T. glabrata WSH-IP303 were screened for mutants that require acetate for complete growth on glucose minimum medium. A mutant, T. glabrata CCTCC M202019, produced pyruvate 21% higher than that of the parent strain and was genetically stable in flask cultures, was selected as a working strain. To elucidate the metabolic changes that led to the increase of pyruvate production, the activities of enzymes that involved in pyruvate-related metabolic pathways of the mutant and the parent strain were determined. Enzymatic analysis revealed that, compared with the parent strain WSH-IP303, the activity of pyruvate decarboxylase of the mutant strain CCTCC M202019 decreased by roughly 40%, while the activity of acetyl-CoA synthetase of the latter increased by 103.5% or 57.4%, respectively, in the presence or absence of acetate. When 6 g/L sodium acetate was added to the medium, pyruvate production by the mutant strain CCTCC M202019 reached 68.7 g/L at 62 h (yield on glucose, 0.651 g/g) in fermentations performed in a 7-L jar fermentor, indicating the shortage of cytosolic acetyl-CoA resulted from the disruption of pyruvate decarboxylase was properly compensated by the increase of the activity of acetyl-CoA synthetase.

Acetates↗

PubMed2005

[Radiotherapy on neck for nasopharyngeal carcinoma patients with negative cervical lymph node].

BACKGROUND & OBJECTIVE: Nasopharyngeal carcinoma (NPC) patients with negative cervical lymph node (N0-NPC) account for 20% -30% of all NPC patients. Prophylactic irradiation to the upper neck is a criterion of treatment for these patients. But some authors suggest to prophylactically irradiate the the whole neck. This study was to analyze and compare long-term outcomes of the N0-NPC patients treated by prophylactic irradiation to the upper neck and to the whole neck, and explore radiotherapy on neck for N0-NPC patients. METHODS: A total of 178 N0-NPC patients, proved by pathology, were treated in our hospital from Jul. 1998 to Dec. 1999. Of the 178 patients, 88 received prophylactic irradiation to the upper neck (upper neck group), 90 received prophylactic irradiation to the whole neck (whole neck group). Kaplan-Meier method and log-rank test were used to analyze and compare survival rate of the 2 groups. Cox model was used to study prognostic factors of N0-NPC. RESULTS: The 1-, 3-, and 5-year overall survival rates were 98.9%, 90.9%, and 80.7% in upper neck group, and 97.8%, 80.0%, and 71.1% in whole neck group (P = 0.224). The 1-, 3-, and 5-year disease-free survival rates were 93.2%, 80.7%, and 77.3% in upper neck group, and 85.6%, 68.9%, and 64.4% in whole neck group (P = 0.163). The incidence of cervical lymph nodes recurrence was 1.14% in upper neck group, and 1.09% in whole neck group (P> 0.05). Multivariate analysis showed that gender, T stage, and short-term outcome were independent prognostic factors of N0-NPC. CONCLUSION: Prophylactic irradiation to upper neck is recommended for N0-NPC patients.

Adult↗

PubMed2005

[Spindle cell squamous carcinoma of the oral cavity: report of 2 cases].

Two cases with spindle cell squamous carcinoma were reported in this paper. The clinical, histopathologic features, therapy and prognosis were discussed. These tumors probably represented a heterogeneous group of squamous cell carcinoma whose components required either an identifiable squamous cell carcinoma or evidence of epithelial differentiation in the spindle cell. The clinical features were as follow: presents a male predominance among 60 to 70 years and site predilection for the low lip, tongue and gingiva, more aggressive and easy lymphatic metastases. Wide surgical excision, alone or with radical neck dissection was the most successful therapeutic modality. Local recurrence, lymphatic metastases and the depth of tumor invasion into underlying structures were found to be reliable prognostic indicators, the prognosis was dismal.

Carcinoma↗

PubMed2005

[Modeling for prediction of arabinoxylans solubilization and endo-xylanase random attacking during mashing].

A model describing the solubilization of arabinoxylans and degradation by endo-xylanase random attacking during mashing was developed. The model was expected to predict the arabinoxylans concentration in wort at the settings of different initial value and mashing parameters for diminishing the negative effects of arabinoxylans on brewing. Results showed that the modeling errors range for the final concentration of arabinoxylans in wort was -9.5% to +13.6%. The model prediction accuracy for industrial scale mashing process was lower than that in laboratory scale. The errors were given 16.8% and 17.9%, respectively. The simulation results showed that arabinoxylans concentration was increased with the increase of mashing-in temperature, but it was decreased with prolonging the mashing-in time. The effect of initial arabinoxylans in malt on arabinoxylans concentration in wort was more remarkable than that of endo-xylanase activity in grist.

Endo-1,4-beta Xylanases↗

PubMed2005

[Impact of dose boost in skull base on recurrence of stage T4 nasopharyngeal carcinoma].

BACKGROUND & OBJECTIVE: The recurrence rate in skull base is high for nasopharyngeal carcinoma (NPC) patients with cavernous sinus or/and sphenoid sinus involvement. This study was conducted to explore the impact of dose boost in skull base on the recurrence in skull base and survival of NPC patients with cavernous sinus or/and sphenoid sinus involvement. METHODS: A total of 120 stage T4 NPC patients with cavernous sinus or/and sphenoid sinus involvement proved by histopathology and computed tomography (CT) were treated in our hospital from Oct. 1996 to Nov. 1998. The irradiation dose was (71.55+/-3.09) Gy in nasopharynx and (58.95+/-6.16) Gy in neck. Of the 120 patients, 27 received irradiation (6-10 Gy) in skull base after radiotherapy (boost group), 93 did not receive irradiation in skull base (control group). Fifty-three patients, 41 in control group and 12 in boost group, received cisplatin-based chemotherapy for 1-3 cycles. The survival rates and the recurrence of the 2 groups were calculated by Kaplan-Meier method and log-rank test. RESULTS: The clinical characteristics of patients were similar in the 2 groups. The 1-, 3-, 5-year skull base control rates were significantly higher in boost group than in control group (100% vs. 93.4%, 91.8% vs. 76.4%, and 86.8% vs. 65.1%, respectively, P=0.045). The 1-, 3-, 5-year disease-freely survival rates were slightly higher in boost group than in control group (85.2% vs. 75.3%, 59.3% vs. 45.2%, and 51.9% vs. 31.2%, respectively, P=0.084). The median disease-freely survival time was longer in boost group than in control group (60 months vs. 30 months). The prevalences of irradiation-induced brain damage were 7.4% in boost group and 4.3% in control group with no significant difference (P=0.514). CONCLUSION: Dose boost in skull base can reduce the recurrence of stage T4 NPC in skull base and tends to enhance the disease-freely survival rate for NPC patients with cavernous sinus or/and sphenoid sinus involvementû it is recommended to such patients.

Adult↗

PubMed2005

[Influence of expression of transglutaminase on the growth of Lactococcus lactis].

To improve the aerobic growth performance of Lactococcus lactis subsp. cremoris NZ9000, the gene mtg encoding the mature microbial transglutaminase was amplified from the chromosomal DNA of Streptoverticillium mobaraense and then cloned into the nisin-inducible expression vector pNZ8148. The resulting plasmid pFL001 was transformed into strain NZ9000 by electroporation. Compared with strain NZ9000 harboring pNZ8148 (the control strain), strain NZ9000 harboring pFL001 (the recombinant strain) had a remarkably improved aerobic growth performance. When grown aerobically under non-pH-controlled conditions, the maximal biomass of the recombinant strain reached 4.13 g/L, which was 11-fold higher than the growth of the control strain (0.34 g/L). When grown aerobically with the pH controlled at 6.5 +/- 0.1, the maximal biomass of the recombinant strain reached 4.73 g/L, which was an 80% increase compared with the growth of the control strain. In addition, the efficiency of biomass synthesis relative to glucose consumption (Y(x/s)) of the recombinant strain, 71.7 g of biomass per mol of glucose, was 1.6-fold higher than that of the control strain. The significantly improved growth performance of the recombinant strain might be attributed to the expression of mtg in the recombinant strain, which might increase intracellular pH and save part of the energy(ATP) that was originally used for pumping the cytoplasmic H+, and as a consequence, the energy used for growth increased accordingly.

Hydrogen-Ion Concentration↗

PubMed2005

[Torulopsis glabrata neomycin-resistant mutant abolishes pyruvate production with enhancement of glucose consumption rate].

To further increase the rate of glucose consumption by multi-vitamin auxotrophic yeast Torulopsis glabrata. A neomycin-resistant mutant N07, with the activity of F1-ATPase decreased roughly 35% but glucose consumed per cell was increased 38% than that of parent strain, was breed based on analysis of energy metabolic pathway. The typical inhibitors of F1F0-ATPase, DCCD, NaN3 and neomycin, depressed the F1-ATPase activity of parental strain but no effect on that of mutant strain. Strain N07 was cultured in a pyruvate fermentation medium containing 100g/L of glucose using flask. It was found that the rate of glucose consumption and pyruvate production were higher by 34% and 42.9% in the mutant than in the parent, respectively. However, the rate and yield of growth (about 24%) of the mutant was lower than that of the parent. The content of intracellular ATP of the mutant also decreased 23.7% than that of the parent. The activities of key enzymes in glycolytic pathway and electron transfer chain of the mutant and the parent were determined. Enzymatic analysis revealed that, compared with the parent strain CCTCC M202019. The activities of key enzymes, phosphofructokinase, pyruvate kinase, glyceraldyde-3-phosphate dehydrogenase of the mutant N07 increased 63.7%, 28.8% and 14.4%, respectively, all the key enzymes of electron transfer chain in the mutant N07 also increased roughly 10%.

Adenosine Triphosphate↗

PubMed2004

Using Lactococcus lactis for glutathione overproduction.

Glutathione and gamma-glutamylcysteine were produced in Lactococcus lactis using a controlled expression system and the genes gshA and gshB from Escherichia coli encoding the enzymes gamma-glutamylcysteine synthetase and glutathione synthetase. High levels of gamma-glutamylcysteine were found in strains growing on chemically defined medium and expressing either gshA alone or both gshA and gshB. As anticipated, glutathione was found in a strain expressing gshA and gshB. The level of glutathione production could be increased by addition of the precursor amino acid cysteine to the medium. The addition of cysteine led to an increased activity of glutathione synthetase, which is remarkable because the amino acid is not a substrate of this enzyme. The final intracellular glutathione concentration attained was 358 nmol mg(-1) protein, which is the highest concentration reported for a bacterium, demonstrating the suitability of engineered L. lactis for fine-chemical production and as a model for studies of the impact of glutathione on flavour formation and other properties of food.

Cloning, Molecular↗

PubMed2004

Analysis of clinical effect of high-intensity focused ultrasound on liver cancer.

AIM: To evaluate the clinical effect of high-intensity focused ultrasound (HIFU) in the treatment of patients with liver cancer. METHODS: HIFU treatment was performed in 100 patients with liver cancer under general anesthesia and by a targeted ultrasound. Evaluation of efficacy was made on the basis of clinical symptoms, liver function tests, AFP, MRI or CT before and after the treatment. RESULTS: After HIFU treatment, clinical symptoms were relieved in 86.6%(71/82) of patients. The ascites disappeared in 6 patients. ALT (95+/-44) U/L and AST (114+/-58) U/L before HIFU treatment were reduced to normal in 83.3%(30/36) and 72.9%(35/48) patients, respectively, after the treatment. AFP was lowered by more than 50% in 65.3%(32/49) patients. After HIFU treatment, MRI or CT findings indicated coagulation necrosis and blood supply reduction or disappearance of tumor in the target region. CONCLUSION: HIFU can efficiently treat the patients with liver cancer. It will offer a significant noninvasive therapy for local treatment of liver tumor.

Adult↗

PubMed2004

Decolorization and biodegradation of dye wastewaters by a facultative-aerobic process.

BACKGROUND: Dye wastewater is one of the main pollution sources of water bodies in China. Conventional biological processes are relatively ineffective for color removal, the development of alternative treatment methods will become important. Our subjective was that of introducing a new biotreatment technology which combined a facultative biofilm reactor (FBR) with an aerobic reactor (AR) to treat a dye wastewater. The efficiencies of color and chemical oxygen demand (COD) removal and the mechanism of dye degradation were investigated. METHODS: The anthraquinone acid dye (acid blue BRLL) concentration, organic loading rate (OLR) and hydraulic retention time (HRT) were varied in the experiments to evaluate the treatment efficiency and process stability. The biodegradation products were detected by infrared (IR) and high performance liquid chromatography and mass spectrometry (HPLC-MS). RESULTS AND DISCUSSION: The results demonstrated that the facultative biofilm process was more effective for decolorization than the anaerobic stage of an anaerobic-aerobic process. Most color removal occurred in the facultative reaction (maximum to 88.5%) and the BOD (biochemical oxygen demand): COD of the FBR effluent increased by 82.2%, thus improving the biodegradability of dyes for further aerobic treatment. The dye concentration, OLR and HRT will be the factors affecting decolorization. Color removal efficiency falls as the influent dye concentration increases, but rises with increased HRT. The infrared and HPLC-MS analyses of the effluents of FBR and AR reveal that the dye parent compound was degraded in each reactor during the process. CONCLUSION: The Facultative-aerobic (F-A) system can effectively remove both color and COD from the dye wastewater. The FBR played an essential role in the process. The average overall color and COD in the system were removed by more than 93.9% and 97.1%, respectively, at an OLR of 1.1 kg COD m(-3) d(-1) and at the HRT of 18-20 hours in the FBR and 4-5 hours in the AR. The color removal mechanism in each reactor was not only a sort of biosorption on the floc materials, but even more an effect of biodegradation, especially in the facultative process. Recommendation and Outlook. In applying the F-A system to treat a dye wastewater, the control of facultative processes and the set up of appropriate operation conditions appear to be critical factors. Also, it is suggested a moderate COD loading rate and about a 24-hour HRT will favor the F-A system.

Bacteria, Aerobic↗

PubMed2004

Glutathione: a review on biotechnological production.

This Mini-Review summarizes the historic developments and technological achievements in the biotechnological production of glutathione in the past 30 years. Glutathione is the most abundant non-protein thiol compound present in living organisms. It is used as a pharmaceutical compound and can be used in food additives and the cosmetic industries. Glutathione can be produced using enzymatic methods in the presence of ATP and its three precursor amino acids (L-glutamic acid, L-cysteine, glycine). Alternatively, glutathione can be produced by direct fermentative methods using sugar as a starting material. In the latter method, Saccharomyces cerevisiae and Candida utilis are currently used to produce glutathione on an industrial scale. At the molecular level, the genes gshA and gshB, which encode the enzymes gamma-glutamylcysteine synthetase and glutathione synthetase, respectively, have been cloned from Escherichia coli and over-expressed in E. coli, S. cerevisiae, and Lactococcus lactis. It is anticipated that, with the design and/or discovery of novel producers, the biotechnological production of glutathione will be further improved to expand the application range of this physiologically and medically important tripeptide.

Adenosine Triphosphate↗

PubMed2004

Pre-germinated conidia of Coniothyrium minitans enhances the foliar biological control of Sclerotinia sclerotiorum.

The relatively slow germination rate of Coniothyrium minitans limits its control efficiency against Sclerotinia sclerotiorum. Pre-germinated conidia of C. minitans enhanced its efficiency significantly: in foliar experiments with oilseed rape, hyphal extension of S. sclerotiorum was inhibited by 68%, while formation of sclerotia was completely inhibited when pre-germinated conidia were applied.

Ascomycota↗

PubMed2004

Production of a novel polygalacturonic acid bioflocculant REA-11 by Corynebacterium glutamicum.

The production of a novel polygalacturonic acid bioflocculant REA-11 from a newly isolated strain, Corynebacterium glutamicum CCTCC M201005, was investigated. Sucrose was chosen as a carbon source for REA-11 production. Complex nitrogen sources containing urea and an organic nitrogen compound enhanced both bacterial growth and REA-11 production, among which urea plus corn steep liquor was shown to be the most efficient combination. A cost-effective medium for REA-11 production mainly comprised 17 g/l sucrose, 0.45 g/l urea, and 5 ml/l corn steep liquor, under which conditions the flocculating activity reached 390 U/ml. The molar ratio of carbon to nitrogen (C/N) significantly affected REA-11 production, where a C/N ratio of 20:1 was shown to be the best. Interestingly, by simultaneously feeding sucrose and urea at a C/N ratio of 20:1 at 24 h of fermentation, REA-11 production (458 U/ml) was enhanced by 17% compared to the control. In a 10 l jar fermentor, lower dissolved oxygen tension was favorable for REA-11 production: a flocculating activity of 520 U/ml was achieved at a kappaLa of 100 h(-1). REA-11 raw product is relatively thermo-stable at acidic pH ranges of 3.0-6.5. Preliminary application studies showed that REA-11 had stronger flocculating activity to Kaolin clay suspension compared to chemical flocculants. In addition, the capability of decolorizing molasses wastewater indicates the industrial potential of this novel bioflocculant.

Carbon↗

PubMed2004

Effects of zearalenone on mRNA expression and activity of cytochrome P450 1A1 and 1B1 in MCF-7 cells.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a ubiquitous pollutant and promoter of carcinogenesis with both estrogenic and antiestrogenic effects in mammal epithelium. Zearalenone (ZEA) is a naturally occurring estrogenic contaminant of moldy feeds and is present in high concentrations in dairy products and cereals. Numerous studies describe a possible correlation between xenoestrogens and breast cancer risk. A potential mechanism for the etiology of breast cancer involves altered cytochrome P450 (CYP) enzymes. Since cocontamination of multiple compounds in our environmental and occupational circumstances likely happens and since few studies have addressed the molecular consequences of combinations of contaminants, we decided to investigate the effects of ZEA on basal and TCDD-induced mRNA expression and enzymic activity of CYP1A1 and CYP1B1 in human breast cancer MCF-7 cells. CYP1A1 enzyme activity was measured by the CYP1A1-referential activity assay, ethoxyresorufin O-deethylase (EROD), in MCF-7 cells. To investigate CYP1B1 activity, we employed the microsomal EROD assay prepared from baculovirus-infected insect cells expressing human cDNA CYP1B1. Reverse transcription-polymerase chain reaction was used to detect mRNA expression of CYP1A1 and CYP1B1 in MCF-7 cells. The results demonstrated that 10nM TCDD could readily induce a significant increase in the enzyme activity and mRNA expression of CYP1A1 in MCF-7 cells and 5 nM estradiol (E2) significantly reduced both basal and TCDD-induced activity and mRNA expression in MCF-7 cells. The same pattern was observed with 50nM ZEA. The estrogen receptor antagonist 4-hydroxytamoxifen could attenuate these inhibitive effects of both E2 and ZEA. Interestingly, Both E2 and ZEA could promote basal and TCDD-induced CYP1B1 activity but with no effect on CYP1B1 mRNA expression. These results suggest that the effect of ZEA on the TCDD-induced CYP1A1 activity and gene expression involved the estrogen receptor pathway and that the increase in the CYP1B1/CYP1A1 ratio underlying the basal or TCDD-treated condition might constitute one of the mechanisms underlying the synergic carcinogenic action of these compounds.

Aryl Hydrocarbon Hydroxylases↗

PubMed2004

Naltrexone does not prevent acquisition or expression of flavor preferences conditioned by fructose in rats.

The effects of the general opioid antagonist, naltrexone, on the acquisition and expression of flavor preferences conditioned by the sweet taste of fructose were examined. Food-restricted rats were trained over eight daily alternating one-bottle sessions (2 h) to drink an 8% fructose solution containing one novel flavor (CS+/F) and a less preferred 0.2% saccharin solution containing a different flavor (CS-/S). Four groups of rats were treated daily with either saline (control group) or naltrexone doses of 0.1, 1.0, or 5.0 mg/kg during training. Preferences were assessed in two-bottle tests with the CS+/S and CS-/S flavors presented in 0.2% saccharin solutions following saline injections. Naltrexone dose-dependently reduced fructose and saccharin intakes during training, confirming the drug's well-known suppressive effect on the intake of sweet solutions. Despite their reduced training intakes, the naltrexone groups displayed preferences for the CS+/S over the CS-/S (72-86%) that were similar to that of the control group (78%). The effect of naltrexone on the expression of the CS+/S flavor preference was evaluated by treating control rats with naltrexone (0.1-5 mg/kg) prior to CS+/S vs. CS-/S choice tests. The drug doses produced a dose-dependent reduction in CS+/S intake but did not significantly attenuate the CS+/S preference. These data are consistent with the relative inability of naltrexone to reduce flavor-flavor conditioning by sucrose in sham-feeding rats and flavor-nutrient conditioning in rats receiving intragastric sucrose infusions. In contrast, dopamine antagonists reduce both sucrose- and fructose-conditioned flavor preferences, which indicates the sensitivity of these conditioning paradigms to neuropharmacological manipulations. These data indicate that the endogenous opioid system, unlike the dopamine system, does not play a major role in either the acquisition or expression of flavor preference learning as measured in two-bottle choice tests.

Animals↗

PubMed2004

Conformational stabilities and structural parameters of (CH3)(n)CH(3-n) CFO molecules.

Variable temperature (-60 to -100 degrees C) studies of the infrared spectra (3500-400 cm(-1)) of propionyl fluoride (CH3CH2CFO) and 2-methylpropionyl fluoride ((CH3)2CHCFO), dissolved in liquid xenon have been recorded. From these data, the enthalpy difference has been determined to be 329 +/- 33 cm(-1) (3.94 +/- 0.39 kJ/mol) for propionyl fluoride with the trans conformer (methyl group eclipsing the oxygen atom) more stable than the gauche form. For 2-methylpropionyl fluoride, the enthalpy difference has been determined to be 297 +/- 30 cm(-1) (3.55 +/- 0.36 kJ/mol) with the gauche conformer (methyl group eclipsing the oxygen atom) more stable than the trans form. From these DeltaH values along with assigned torsional fundamentals for both conformers and accompanying "hot bands" the potential functions governing the conformational interchange have been calculated. Utilizing the infrared data from the xenon solution and ab initio frequency predictions from MP2/6-31G* calculations, a few reassignments of the fundamentals have been made. Ab initio calculations have been carried out with several different basis sets up to MP2/6-311 + G** from which structural parameters and conformational stabilities have been determined. Additionally, force constants, infrared intensities, Raman activities, depolarization ratios, and scaled vibrational frequencies have been determined from MP2/6-31G* calculations. Adjusted structural parameters have been obtained from combined ab initio predicted values and previously reported microwave data. These parameters are compared to those obtained from either the earlier microwave and/or electron diffraction studies. Similar ab initio calculations and structural parameter determinations have been carried out for acetyl fluoride (CH3CFO) and trimethylacetyl fluoride ((CH3)3CCFO) and compared to the corresponding experimental results when appropriate.

Acetates↗