7,175 research outputs found
Yeast metabolism in fresh and frozen dough : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
No full textAuthor also known as SM LovedayFresh bakery products have a very short shelf life, which limits the extent to which manufacturing can be centralised. Frozen doughs are relatively stable and can be manufactured in large volumes, distributed and baked on-demand at the point of sale or consumption. With appropriate formulation and processing a shelf life of several months can be achieved.Shelf life is limited by a decline in proofing rate after thawing, which is attributed to a) the dough losing its ability to retain gas and b) insufficient gas production, i.e. yeast activity. The loss of shelf life is accelerated by delays between mixing and freezing, which allow yeast cells the chance to ferment carbohydrates.This work examined the reasons for insufficient gas production after thawing frozen dough and the effect of pre-freezing fermentation on shelf life. Literature data on yeast metabolite dynamics in fermenting dough were incomplete. In particular there were few data on the accumulation of ethanol, a major fermentation end product which can be injurious to yeast.Doughs were prepared in a domestic breadmaker using compressed yeast from a local manufacturer and analysed for glucose, fructose, sucrose, maltose and ethanol. Gas production after thawing declined within 48 hours of frozen storage. This was accelerated by 30 or 90 minutes of fermentation at 30;C prior to freezing.Sucrose was rapidly hydrolysed and yeast consumed glucose in preference to fructose. Maltose was not consumed while other sugars remained. Ethanol, accumulated from consumption of glucose and fructose, was produced in approximately equal amounts to CO2, indicating that yeast cells metabolised reductively.Glucose uptake in fermenting dough followed simple hyperbolic kinetics and fructose uptake was competitively inhibited by glucose. Mathematical modelling indicated that diffusion of sugars and ethanol in dough occurred quickly enough to eliminate solute gradients brought about by yeast metabolism
Activation of the Notch pathway in Down syndrome: cross-talk of Notch and APP.
No full textABSTRACT Down syndrome (DS) patients suffer
from mental retardation, but also display enhanced
-APP production and develop cortical amyloid
plaques at an early age. As -APP and Notch are both
processed by -secretase, we analyzed expression of the
Notch signaling pathway in the adult DS brain and in a
model system for DS, human trisomy 21 fibroblasts by
quantitative PCR. In adult DS cortex we found that
Notch1, Dll1 and Hes1 expression is up-regulated.
Moreover, DS fibroblasts and Alzheimer disease cortex
also show overexpression of Notch1 and Dll1, indicating
that enhanced -APP processing found in both DS
and AD could be instrumental in these changes. Using
pull-down studies we could demonstrate interaction of
APP with Notch1, suggesting that these transmembrane
proteins form heterodimers, but independent of
-secretase. We could demonstrate binding of the intracellular
domain of Notch1 to the APP adaptor
protein Fe65. Furthermore, activated Notch1 can transactivate
an APP target gene, Kai1, and vice versa,
activated APP can trans-activate the classical Notch
target gene Hes1. These data suggest that Notch expression
is activated in Down syndrome, possibly
through cross-talk with APP signaling. This interaction
might affect brain development, since the Notch pathway
plays a pivotal role in neuron-glia differentiation.—
Activation of the Notch pathway in Down syndrome:
cross-talk of Notch and APP. Fischer, D. F., van Dijk,
R., Sluijs, J. A., Nair, S. M., Racchi, M., Levelt, C. N.,
van Leeuwen, F. W., Hol, E. M. FASEB J. 19, 1451–1458
(2005
Converting SrI <sub>2</sub> :Eu <sup>2+</sup> into a near infrared scintillator by Sm <sup>2+</sup> co-doping
No full text The luminescence and scintillation properties of SrI 2 single crystals doped with 5% Eu 2+ and 0.05%, 0.2% and 0.5% Sm 2+ are evaluated. X-ray excited and photoluminescence measurements show energy transfer from excited Eu 2+ ions to Sm 2+ ions. At a concentration of 0.5% Sm 2+ , the luminescence consists almost entirely of 740 nm emission from Sm 2+ 5d-4f transitions. Co-doping SrI 2 :5% Eu 2+ with Sm 2+ provides a novel method to bypass the self-absorption problem encountered in large SrI 2 :Eu 2+ crystals and, at the same time, provides a unique near-infrared emitting scintillator with a light yield of approximately 40,000 photons/MeV. Accepted Author ManuscriptRST/Fundamental Aspects of Materials and EnergyRST/Luminescence Material
'Laws 'Needefull in Later to be Abrogated': Intersex and the Sources of Christian Theology
No full textThis is the author accepted manuscript. The final version is available from Palgrave Macmillan via the DOI in this record
Introduction: Troubling Bodies?
No full textThis is the author accepted manuscript. The final version is available from Palgrave Macmillan via the DOI in this record
Impaired spliceosomal UsnRNP assembly leads to Sm mRNA down-regulation and Sm protein degradation
No full textSpecialized assembly factors facilitate the formation of many macromolecular complexes in vivo. The formation of Sm core structures of spliceosomal U-rich small nuclear ribonucleoprotein particles (UsnRNPs) requires assembly factors united in protein arginine methyltransferase 5 (PRMT5) and survival motor neuron (SMN) complexes. We demonstrate that perturbations of this assembly machinery trigger complex cellular responses that prevent aggregation of unassembled Sm proteins. Inactivation of the SMN complex results in the initial tailback of Sm proteins on the PRMT5 complex, followed by down-regulation of their encoding mRNAs. In contrast, reduction of pICln, a PRMT5 complex subunit, leads to the retention of newly synthesized Sm proteins on ribosomes and their subsequent lysosomal degradation. Overexpression of Sm proteins under these conditions results in a surplus of Sm proteins over pICln, promoting their aggregation. Our studies identify an elaborate safeguarding system that prevents individual Sm proteins from aggregating, contributing to cellular UsnRNP homeostasis.</jats:p
Isoforms of U1-70k control subunit dynamics in the human spliceosomal U1 snRNP
No full textMost human protein-encoding genes contain multiple exons that are spliced together, frequently in alternative arrangements, by the spliceosome. It is established that U1 snRNP is an essential component of the spliceosome, in human consisting of RNA and ten proteins, several of which are post- translationally modified and exist as multiple isoforms. Unresolved and challenging to investigate are the effects of these post translational modifications on the dynamics, interactions and stability of the particle. Using mass spectrometry we investigate the composition and dynamics of the native human U1 snRNP and compare native and recombinant complexes to isolate the effects of various subunits and isoforms on the overall stability. Our data reveal differential incorporation of four protein isoforms and dynamic interactions of subunits U1-A, U1-C and Sm-B/B’. Results also show that unstructured post- ranslationally modified C-terminal tails are
responsible for the dynamics of Sm-B/B’ and U1-C and that their interactions with the Sm core are controlled by binding to different U1-70k isoforms and their phosphorylation status in vivo. These results therefore provide the important functional link between proteomics and structure as well as insight into the dynamic quaternary structure of the native U1 snRNP important for its function.This work was funded by: BBSRC (OVM), BBSRC and EPSRC (HH and NM), EU Prospects (HH), European Science Foundation (NM), the Royal Society (CVR), and fellowship from JSPS and HFSP (YM and DAPK respectively)
Unique Sm core structure of U7 snRNPs: assembly by a specialized SMN complex and the role of a new component, Lsm11, in histone RNA processing.
No full textA set of seven Sm proteins assemble on the Sm-binding site of spliceosomal U snRNAs to form the ring-shaped Sm core. The U7 snRNP involved in histone RNA 3' processing contains a structurally similar but biochemically unique Sm core in which two of these proteins, Sm D1 and D2, are replaced by Lsm10 and by another as yet unknown component. Here we characterize this factor, termed Lsm11, as a novel Sm-like protein with apparently two distinct functions. In vitro studies suggest that its long N-terminal part mediates an important step in histone mRNA 3'-end cleavage, most likely by recruiting a zinc finger protein previously identified as a processing factor. In contrast, the C-terminal part, which comprises two Sm motifs interrupted by an unusually long spacer, is sufficient to assemble with U7, but not U1, snRNA. Assembly of this U7-specific Sm core depends on the noncanonical Sm-binding site of U7 snRNA. Moreover, it is facilitated by a specialized SMN complex that contains Lsm10 and Lsm11 but lacks Sm D1/D2. Thus, the U7-specific Lsm11 protein not only specifies the assembly of the U7 Sm core but also fulfills an important role in U7 snRNP-mediated histone mRNA processing
Intrafullerene electron transfers in Sm-containing metallofullerenes: Sm@C-2n (74 <= 2n <= 84)
No full textThe electronic properties of Sm-containing metallofullerenes, Sm@C-74, Sm@C-76 (I, II), Sm@C-78, Sm@C-80, Sm@C-82 (I, II, III) and Sm@C-84 (I, II, III), are characterized by UV-Vis-NIR absorption spectroscopy and electron energy-loss spectroscopy (EELS). the UV-Vis-NIR absorption spectra of Sm@C-74, Sm@C-80, Sm@C-82 (I, II, III) and Sm@C-84 (I, II) are quite similar to those of the corresponding Ca, Sr, Ba, Eu, Tm, Yb-based metallofullerenes. In contrast, the absorption spectra of Sm@C-76 (I, II), Sm@C-78 and Sm@C-84(III) show a novel feature: the onset for Sm@C-78 is observed similar to 2600 nm, which corresponds to a small band gap (similar to0.5 eV). Furthermore, the oxidation states of Sm atom in the various fullerene cages are investigated by EELS, which reveals that the Sm atom takes +2 oxidation state in the fullerene cages. A probable rationale for the tendency to have the Sm2+ state is presented based on a simple thermochemical cycle model. (C) 2001 by Elsevier Science Inc.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000168906500014&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Biochemical Research MethodsBiochemistry & Molecular BiologyComputer Science, Interdisciplinary ApplicationsCrystallographyMathematical & Computational BiologySCI(E)EI30ARTICLE2244-2511
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