Biomedical subjects

Ling Hua

Publications and source records attributed to Ling Hua.

9 recordsLinked to original sources

PubMed2007

Scale-up of enzymatic production of lactobionic acid using the rotary jet head system.

Enzymatic oxidation of lactose to lactobionic acid (LBA) by a carbohydrate oxidase from Microdochium nivale was studied in a pilot-scale batch reactor of 600 L working volume using a rotary jet head (RJH) for mixing and mass transfer (Nordkvist et al., 2003, Chem Eng Sci 58:3877-3890). Both lactose and whey permeate were used as substrate, air was used as oxygen source, and catalase was added to eliminate the byproduct hydrogen peroxide. More than 98% conversion to LBA was achieved. Neither enzyme deactivation nor enzyme inhibition was observed under the experimental conditions. The dissolved oxygen tension (DOT) was constant throughout the tank for a given set of operating conditions, indicating that liquid mixing was sufficiently good to avoid oxygen gradients in the tank. However, at a given oxygen tension measured in the tank, the specific rate of reaction found in the RJH system was somewhat higher than previously obtained in a 1 L mechanically stirred tank reactor (Nordkvist et al., 2007, in this issue, pp. 694-707). This can be ascribed to a higher pressure in the recirculation loop which is part of the RJH system. Compared to mechanically stirred systems, high values of the volumetric mass transfer coefficient, k(L)a, were obtained when lactose was used as substrate, especially at low values of the specific power input and the superficial gas velocity. k(L)a was lower for experiments with whey permeate than with lactose due to addition of antifoam. The importance of mass transfer and of the saturation concentration of oxygen on the volumetric rate of reaction was demonstrated by simulations.

Ascomycota↗

PubMed2006

Enantioselective enzymatic reductions of sterically bulky aryl alkyl ketones catalyzed by a NADPH-dependent carbonyl reductase.

The enantioselective reductions of aryl alkyl ketones, ArC(O)R, with a diverse number of alkyl groups have been achieved with an isolated carbonyl reductase from Sporobolomyces salmonicolor. Of special interest is the observation that ketones with sterically bulky alkyl groups could be reduced to the corresponding alcohols in excellent optical purity. An unusual alkyl chain-induced enantiopreference reversal was observed but was shown to be consistent with the enzyme-substrate docking calculations.

Alcohol Oxidoreductases↗

PubMed2006

Unexpected stereorecognition in nitrilase-catalyzed hydrolysis of beta-hydroxy nitriles.

Biocatalytic enantioselective hydrolysis of beta-hydroxy nitriles to corresponding (S)-enriched beta-hydroxy carboxylic acids has been achieved for the first time by an isolated nitrilase bll6402 from Bradyrhizobium japonicum USDA110. This offers a new "green" approach to optically pure beta-hydroxy nitriles and beta-hydroxy carboxylic acids. The observed remote stereorecognition is surprising because this nitrilase shows no enantioselectivity for the hydrolysis of alpha-hydroxy nitriles such as mandelonitrile.

Aminohydrolases↗

PubMed2006

Stereoselective ketone reduction by a carbonyl reductase from Sporobolomyces salmonicolor. Substrate specificity, enantioselectivity and enzyme-substrate docking studies.

In our effort to search for effective carbonyl reductases, the activity and enantioselectivity of a carbonyl reductase from Sporobolomyces salmonicolor have been evaluated toward the reduction of a variety of ketones. This carbonyl reductase (SSCR) reduces a broad spectrum of ketones including aliphatic and aromatic ketones, as well as alpha- and beta-ketoesters. Among these substrates, SSCR shows highest activity for the reduction of alpha-ketoesters. Aromatic alpha-ketoesters are reduced to (S)-alpha-hydroxy esters, while (R)-enantiomers are obtained from the reduction of aliphatic counterparts. This interesting observation is consistent with enzyme-substrate docking studies, which show that hydride transfer occurs at the different faces of carbonyl group for aromatic and aliphatic alpha-ketoesters. It is worthy to note that sterically bulky ketone substrates, such as 2'-methoxyacetophenone, 1-adamantyl methyl ketone, ethyl 4,4-dimethyl-3-oxopentanoate and ethyl 3,3-dimethyl-2-oxobutanoate, are reduced to the corresponding alcohols with excellent optical purity. Thus, SSCR possesses an unusually broad substrate specificity and is especially useful for the reduction of ketones with sterically bulky substituents.

Alcohol Oxidoreductases↗

PubMed2006

Stereoselective enzymatic synthesis of chiral alcohols with the use of a carbonyl reductase from Candida magnoliae with anti-Prelog enantioselectivity.

In our effort to search for carbonyl reductases with anti-Prelog enantioselectivity, the activity and enantioselectivity of a carbonyl reductase from Candida magnoliae have been examined with various ketones of diverse structures. This carbonyl reductase catalyzed the reduction of a series of ketones, alpha- and beta-ketoesters, to anti-Prelog configurated alcohols in excellent optical purity. The usefulness of this carbonyl reductase has been demonstrated by synthesis of several chiral alcohol intermediates of pharmaceutical importance.

Alcohol Oxidoreductases↗

PubMed2006

Lanosterol biosynthesis in plants.

Plants biosynthesize sterols from cycloartenol using a pathway distinct from the animal and fungal route through lanosterol. Described herein are genome-mining experiments revealing that Arabidopsis encodes, in addition to cycloartenol synthase, an accurate lanosterol synthase (LSS)--the first example of lanosterol synthases cloned from a plant. The coexistence of cycloartenol synthase and lanosterol synthase implies specific roles for both cyclopropyl and conventional sterols in plants. Phylogenetic reconstructions reveal that lanosterol synthases are broadly distributed in eudicots but evolved independently from those in animals and fungi. Novel catalytic motifs establish that plant lanosterol synthases comprise a third catalytically distinct class of lanosterol synthase.

Arabidopsis↗

PubMed2005

Long-term outcome and mortality trends in early-stage, Grade 1-2 follicular lymphoma treated with radiation therapy.

PURPOSE: To analyze long-term outcomes and causes of death in patients receiving radiation therapy (RT) for localized, low-grade follicular lymphoma. METHODS AND MATERIALS: Between 1972 and 2000, 106 patients with Stage I-II, Grade 1-2 follicular lymphoma received RT alone or radiation and chemotherapy (RT/CT). Seventy-four percent had Stage I, and 26% had Stage II disease. Seventy-six percent received RT alone, and 24% received combined RT/CT. Second malignancy rates were compared with an age- and sex-matched population. RESULTS: Median follow-up was 12 years. Median survival time was 19 years. The 5-, 10-, and 15-year overall survival (OS) rates were 93%, 75%, and 62%, respectively. Age > or = 60 was the only significant adverse prognostic factor with respect to OS. There were 35 deaths, 20 of which were attributable to lymphoma. Freedom from treatment failure (FFTF) rates at 5, 10, and 15 years were 72%, 46%, and 39%, respectively. Forty-seven patients (48%) relapsed. Tumor size > 3 cm was the only significant adverse factor for FFTF. Observed incidence of second malignancy did not significantly exceed expected incidence. CONCLUSIONS: Although patients with early-stage, low-grade follicular lymphoma have long median survival, the leading cause of death remains lymphoma. However, patients receiving RT do not have significantly elevated cumulative incidence of second malignancy.

Adult↗

PubMed2005

Radiation therapy for orbital lymphoma.

PURPOSE: To describe radiation techniques and evaluate outcomes for orbital lymphoma. METHODS AND MATERIALS: Forty-six patients (and 62 eyes) with orbital lymphoma treated with radiotherapy between 1987 and 2003 were included. The majority had mucosa-associated lymphoid tissue (48%) or follicular (30%) lymphoma. Seventeen patients had prior lymphoma at other sites, and 29 had primary orbital lymphoma. Median follow-up was 46 months. RESULTS: The median dose was 30.6 Gy; one-third received <30 Gy. Electrons were used in 9 eyes with disease confined to the conjunctiva or eyelid, and photons in 53 eyes with involvement of intraorbital tissues to cover entire orbit. Local control rate was 98% for all patients and 100% for those with indolent lymphoma. Three of the 26 patients with localized primary lymphoma failed distantly, resulting in a 5-year freedom-from-distant-relapse rate of 89%. The 5-year disease-specific and overall survival rates were 95% and 88%, respectively. Late toxicity was mainly cataract formation in patients who received radiation without lens block. CONCLUSIONS: A dose of 30 Gy is sufficient for indolent orbital lymphoma. Distant relapse rate in patients with localized orbital lymphoma was lower than that reported for low-grade lymphoma presenting in other sites. Orbital radiotherapy can be used for salvage of recurrent indolent lymphoma.

Adult↗

PubMed2003

[Clinical study of yishen jianpi yangxue tongli therapy in treating polycystic ovary syndrome].

OBJECTIVE: To observe the effect of Yishen Jianpi Yangxue Tongli Therapy (YJYTT) in treating polycystic ovary syndrome (PCOS) and to explore the therapeutic mechanism of YJYTT. METHODS: One hundred and seven PCOS patients with syndrome differentiation of TCM as Pi-Shen Yang deficiency were randomly divided into two groups, the treated group (n = 76) was treated with Chinese herbal medicine, while the control group (n = 31) was treated by clomiphen. The therapeutic effect in both groups and the change of body mass index (BMI), Ferriman-Gallway (F-G) score, serum sex hormones and serum oral glucose tolerance test (OGTT) before and after treatment were observed. RESULTS: The comparison of total effective rate between two groups was insignificantly different, but the pregnancy rate of the treated group (65.7%) was markedly higher than that of control group (25.0%, P < 0.01). Also, significant difference was shown in the aspect of BMI, F-G score, serum testosterone (T), luteinizing hormone (LH) and OGTT, etc. between the two groups (P < 0.05). CONCLUSION: The YJYTT could markedly improve the clinical symptoms and pregnancy rate of PCOS patients, particularly showing good effect to the clomiphen resistant patients. The mechanism possibly was due to its regulation on hypothalamus-pituitary-ovarium axis and reducing the insulin resistance.

Adult↗