3,237 research outputs found
The Mutual Interpretation of Active and Passive Microwave Sensor Outputs
Mutual interpretation of active and passive microwave sensor output
Radar backscattering data for surfaces of geological interest
Radar backscattering data for surfaces of geological interes
High performance microbiological transformation of L-tyrosine to L-dopa by Yarrowia lipolytica NRRL-143
<p>Abstract</p> <p>Background</p> <p>The 3,4-dihydroxy phenyl L-alanine (L-dopa) is a drug of choice for Parkinson's disease, controlling changes in energy metabolism enzymes of the myocardium following neurogenic injury. <it>Aspergillus oryzae </it>is commonly used for L-dopa production; however, potential improvements in ease of handling, growth rate and environmental impact have led to an interest in exploiting alternative yeasts. The two important elements required for L-dopa production are intracellular tyrosinases (thus pre-grown yeast cells are required for the transformation of L-tyrosine to L-dopa) and L-ascorbate, which acts as a reducing agent.</p> <p>Results</p> <p>Pre-grown cells of <it>Yarrowia lipolytica </it>NRRL-143 were used for the microbiological transformation of L-tyrosine to L-dopa. Different diatomite concentrations (0.5ā3.0 mg/ml) were added to the acidic (pH 3.5) reaction mixture. Maximum L-dopa biosynthesis (2.96 mg/ml L-dopa from 2.68 mg/ml L-tyrosine) was obtained when 2.0 mg/ml diatomite was added 15 min after the start of the reaction. After optimizing reaction time (30 min), and yeast cell concentration (2.5 mg/ml), an overall 12.5 fold higher L-dopa production rate was observed when compared to the control. Significant enhancements in Y<sub>p/s</sub>, Q<sub>s </sub>and q<sub>s </sub>over the control were observed.</p> <p>Conclusion</p> <p>Diatomite (2.0 mg/ml) addition 15 min after reaction commencement improved microbiological transformation of L-tyrosine to L-dopa (3.48 mg/ml; p ā¤ 0.05) by <it>Y. lipolytica </it>NRRL-143. A 35% higher substrate conversion rate was achieved when compared to the control.</p
Spin transition in GdN@C, detected by low-temperature on-chip SQUID technique
We present a magnetic study of the GdN@C molecule, consisting of a
Gd-trimer via a Nitrogen atom, encapsulated in a C cage. This molecular
system can be an efficient contrast agent for Magnetic Resonance Imaging (MRI)
applications. We used a low-temperature technique able to detect small magnetic
signals by placing the sample in the vicinity of an on-chip SQUID. The
technique implemented at NHMFL has the particularity to operate in high
magnetic fields of up to 7 T. The GdN@C shows a paramagnetic
behavior and we find a spin transition of the GdN structure at 1.2 K. We
perform quantum mechanical simulations, which indicate that one of the Gd ions
changes from a state () to a state (), likely due to a charge transfer between the C cage and the ion
Thymic Involution in Viable Motheaten (meĻ ) Mice is Associated with a Loss of Intrathymic Precursor Activity
Mice homozygous for the viable motheaten (meĻ
) allele manifest abnormalities in
thymocytopoiesis, are severely immunodeficient, and develop autoimmune disorders
early in life. Premature thymic involution occurs in meĻ
/meĻ
mice, and their bone marrow
prothymocytes are unable to repopulate the thymus of adoptive recipients following
intravenous (i.v.) transfer. However, analysis of thymocytopoiesis following intrathymic
(i.t.) adoptive transfer of bone marrow from meĻ
/meĻ
mice demonstrates the presence of
normal numbers of prothymocytes. To investigate intrathymic development in meĻ
/meĻ
mice, we determined intrathymic precursor cell number and activity. Dual labeling
analyses showed that an involuted meĻ
/meĻ
thymus is relatively enriched (fivefold) in
CD4ā CD8ā thymocytes (intrathymic precursor phenotype) compared with wild-type
(+/+) thymus. However, thymocytes from meĻ
/meĻ
mice were deficient in precursor
activity when adoptively transferred i.t. into irradiated recipients. Thymocytes
recovered from the involuted thymus of aged or steroid-treated normal mice also
displayed reduced precursor activity. However, the phenotypic profile of thymocyte
subsets from steroid-treated mice was enriched in single positive cells (mature
phenotype) and was distinctly different from the subset distribution of thymocytes in
meĻ
/meĻ
and aged mice. These results suggest that intrathymic precursor activity in
meĻ
/meĻ
mice is decreased, and may be reflective of decreased prothymocyte seeding to
the thymus in vivo, In addition, the results suggest that the thymic involution in meĻ
/meĻ
mice is not due solely to effects of corticosteroids
Lack of Peripherally Induced Tolerance to Established Skin Allografts in Immunologically Reconstituted Scid Mice
The mechanism by which the antigen-specific immune system distinguishes between
foreign antigens (toward which it mounts an immune response) and self-antigens (of
which it is tolerant) is not completely understood. Studies using āsuperantigensā and
transgenic mice have allowed investigations into some of the mechanisms of clonal
deletion, anergy, and peripheral tolerance. In the present report, we have attempted to
develop a new model system to investigate the possible mechanism(s) of peripheral
tolerance to allografts. In this system, skin grafts from C57BL/6J (B6; H-2b mice are
grafted onto T- and B-lymphocyte-deficient C.B-17-scid/scid (H-2d; hereafter referred to
as scid) mice. Because of their lack of functional lymphocytes, the scid mice readily
accept the allogeneic skin grafts. After the allografts healed, the scid mice were
reconstituted with T-cell-deficient fetal liver from coisogeneic C.B-17-ā¤/ā¤ mice or bone
marrow from weanling congenitally athymic BALB/c-nu/nu (H-2d; hereafter referred to
as nude) mice. Upon immunological reconstitution, the scid mice reiected the established
B6 skin allografts, suggesting that an immune system developing in the presence of an
intact peripheral skin allograft fails to develop tolerance to the peripheral allograft. This
model system may be useful for the study of the mechanisms required for the induction
of peripheral tolerance
A sequence based synteny map between soybean and Arabidopsis thaliana
BACKGROUND: Soybean (Glycine max, L. Merr.) is one of the world's most important crops, however, its complete genomic sequence has yet to be determined. Nonetheless, a large body of sequence information exists, particularly in the form of expressed sequence tags (ESTs). Herein, we report the use of the model organism Arabidopsis thaliana (thale cress) for which the entire genomic sequence is available as a framework to align thousands of short soybean sequences. RESULTS: A series of JAVA-based programs were created that processed and compared 341,619 soybean DNA sequences against A. thaliana chromosomal DNA. A. thaliana DNA was probed for short, exact matches (15 bp) to each soybean sequence, and then checked for the number of additional 7 bp matches in the adjacent 400 bp region. The position of these matches was used to order soybean sequences in relation to the A. thaliana genome. CONCLUSION: Reported associations between soybean sequences and A. thaliana were within a 95% confidence interval of e(-30 )ā e(-100). In addition, the clustering of soybean expressed sequence tags (ESTs) based on A. thaliana sequence was accurate enough to identify potential single nucleotide polymorphisms (SNPs) within the soybean sequence clusters. An EST, bacterial artificial chromosome (BAC) end sequence and marker amplicon sequence synteny map of soybean and A. thaliana is presented. In addition, all JAVA programs used to create this map are available upon request and on the WEB
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