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1.
Barley -amylase was purified by ammonium sulfate fraction, ion-exchange, ultrafiltration, and gel filtration to homogeneity. The purified enzyme was partially digested with trypsin, and the reaction mixture was applied to a cyclohepta-amylose epoxy Sepharose 6B column. Bound fragments were eluted by free cyclohepta-amylose, lyophilized, and separated on Tricine gels. Four fragments were shown to interact with -cyclodextrin. The fragment that could be identified on the gel with the lowest molecular weight (11 kDa) was electroblotted onto PVDF membrane for sequencing. The N-terminal sequence of this fragment was determined with the N-terminal amino acid corresponding to Ala283 in the whole protein. The trypsin cleavage was at Lys282/Ala283 and the C-terminal cleavage occurred at Lys354/Ile355 to give a fragment size of 11 kDa as estimated by SDS-PAGE. The fragment would be located at the C-terminal region, forming a majority of the antiparallel -sheets in domain C and the 7-and 8-helices of the (/)8 domain. 相似文献
2.
Computational techniques have become important tools in the preliminary stages of the design of new molecules. The mutual arrangements of interacting molecular parts and the required accessibility of important reactive groups on the peripheral regions of possible new molecules can be tested by computational means before the expensive and often complex synthetic methods are used to the actual construction of these molecules. There are some common features involved in the computational representation of molecular fragments and the synthetic methodologies used in the process of incorporating actual molecular fragments in such engineered molecules. One trend that appears to link these two approaches is based on the following observation: the greater local autonomy is shown by the calculated electron density contribution of a given molecular fragment, the more likely that this fragment can be regarded as a suitable building block of the molecule, and it is also more likely that there are convenient synthetic methods for the delivery of this fragment to its desired target location in the new molecule to be synthesized. For a precise formulation of this statement, a new concept, the degree of molecular fragment autonomy is introduced, using the inherent properties of molecular electron densities. 相似文献
3.
In this paper we analyse a stochastic model for invertebrate predation taking account of the predator's satiation. This model approximates Holling's hungry mantid model when handling time is negligible (see Part I). For this model we derive equations from which we can calculate the functional response and the variance of the total catch. Moreover we study a number of approximations which can be used to calculate these quantities in practical cases in a relatively simple manner.List of Notation
a
rate constant of digestion
-
b
maximum of rate constant of prey encounter in the mantid
-
c
satiation threshold for search
-
c
satiation threshold for pursuit in the mantid
-
c
i
(w1/2(N- N)i)
-
expectation operator
-
f
rate of change of satiation during search
-
F
functional response: mean number of prey eaten per unit of time
-
g
rate constant of prey capture
-
h
probability generating function of N conditional on S = s times p
- H
probability generating function of N
- mi
1
-
n, N
number of prey caught
-
p
probability density of S
- pn
simultaneous probability (density) of N and S
-
q
probability of strike success
-
r
dummy variable in generating function
-
s, S
satiation
-
T
s
search time
-
T
d
digestion time
-
v
asymptotic rate of increase of var v
-
V
asymptotic rate of increase of var N
-
w
weight of edible part of prey
-
W
standard Wiener process
-
x
prey density
- z
(N{S = s}-N)p
-
rate constant of prey escape time maximum pursuit time
-
(v{S = + w
1/2}-v)
-
present time as a fraction of the time from the start to the end of the experiment
-
hazard rate of T
s
-
mean time between (downward) passages of S through c
-
v
w–1/2(N-)
-
edible prey biomass density
-
probability density of , number pi
-
parameter of Weibull distribution of T
s = (1/2acx(-g(c)))1/2
-
w–1/2(S -)
-
satiation in the guzzler approximation: solution to d/dt = f() + g(), (0)=S(0).
-
biomass functional response: wF
-
total biomass catch in the guzzler approximation: solution to d/dt = g(), (0) = 0 相似文献
4.
W. J. Schmidt 《Cell and tissue research》1966,73(4):475-487
Zusammenfassung Kegel und Säulen der Schwanen-Eischale hinterlassen am Querschliff nach Entkalkung mit EDTA organisches (mucoproteides) Material als ein zusammenhängendes Gerüst, das sich mit Thionin metachromatisch färbt; ohne Demineralisierung oder wenigstens Anätzung bleibt Thionin an Schliffen und Bruchkanten der Schale wirkungslos. Das Lichtmikroskop zeigt an Schliffen nichts von dem organischen Material, es wurde während des Kristallwachstums fein zerteilt in Gitterlücken des Schalencalcits eingeschlossen. Es findet sich am stärksten angehäuft an den äueren und inneren Oberflächen der Kristall-individuen. In den Kegeln ist das Gerüst radial ausgebildet als die Loculi der Keile, und konzentrisch geschichtet, entsprechend den Lagen der Globularinklusionen, um deren jede herum Verdichtung der organischen Substanz statthat. In den inneren Säulen folgt das organische Gerüst dem Rhombenmuster; die äueren Säulen sind arm an organischer Substanz, hier verbleibt nach der Entkalkung eine dünne laterale Oberflächenschicht.
Summary The cones and columns of the swans egg shell leave behind after decalcification with EDTA an organic (mucoproteid) material in form of a continuous frame work stainable metachromatically with thionine. Without demineralisation or at least etching, thionine proves ineffectual in ground sections or breaking edges of the shell. In ground sections the light microscope demonstrates nothing of the organic material: it was inclosed during the crystal growth in submicroscopical lattice gaps of the calcite individuals. The organic material is chiefly accumulated in the outer and inner surfaces of the crystals. In the cones the organic frame work is developed radially as the loculi of the wedges and concentrically layered corresponding with the globular inclusions, concentrated in the circumference of each. In the inner columns the organic material follows to the rhomb pattern. The outer columns after decalcification only leave behind a thin lateral organic sheath.相似文献
5.
Yanagawa Yuchio Kobayashi Takashi Ohnishi Motoko Kobayashi Takayasu Tamura Shinri Tsuzuki Teruhisa Sanbo Makoto Yagi Takeshi Tashiro Fumi Miyazaki Jun‐ichi 《Transgenic research》1999,8(3):215-221
Gene targeting in embryonic stem (ES) cells via homologous recombination can occur at very low frequency. In order to enrich homologous recombinants before screening, a negative selection marker, such as thymidine kinase (TK) and diphtheria toxin A fragment (DTA), has been commonly used. In this study, we developed a negative selection marker using DTA gene with polyadenylation signal and it was designated DTApA. To determine the difference in targeting efficiency of the negative selections, we constructed three different targeting vectors for each negative selection (first, TK at the 3 end, second, TK at both the 5 and 3 ends <2 X TK>, and third, DTApA at the 5 end of the homologous sequences). Gene targeting experiments using these constructs clearly showed that negative selection using DTApA was more efficient than that using TK for homologous recombination and that negative selection using DTApA was as efficient as that using 2 X TK. Considering the fact that the use of DTApA is more convenient for construction of targeting vectors than that of 2 X TK, DTApA is an efficient negative selection marker.In addition, we examined long and accurate PCR (LAPCR) for screening gene targeted clones. The use of LAPCR with genomic DNAs from ES cell clones facilitated simple detection of homologous recombinants, suggesting that the screening with LAPCR is compatible with the use of longer homologous sequences of both arms in vector design. Our results indicate that the use of DTApA for negative selection together with the application of LAPCR for screening ensures efficient and timesaving screening for homologous recombinants. 相似文献
6.
The diversity of isoforms of retinoic acid (RA) receptors (RARs) and of DNA sequences of retinoic acid-responsive elements (RAREs) suggests the existence of selectivities in the RAR/RARE recognition or in the subsequent gene modulation. Such selectivities might be particularly important for RAREs involved in positive feedback, eg. the RAR RARE. In the present work we found that in several epithelial cell lines, reporter constructs containing the RAR RARE linked to the HSV-tk promoter were transactivated in the presence of RA by endogenous RARs and co-transfected RAR1 and RAR2 isoforms, but not by RAR1. On the contrary, this latter isoform behaved towards the RAR RARE as an inhibitor of the transactivation produced by endogenous RARs and by cotransfected RAR1 and RAR2. RAR1 also behaved as an antagonist of the transactivation produced by cotransfected RXR. The natural RAR gene promoter or RAR RARE tk constructs were not activated by the endogenous receptors of normal human keratinocytes (NHK), which are known to contain predominantly RAR1. It was, however, possible to activate to a certain extent RAR RARE-reporter constructs in NHK by co-transfecting RAR1, RAR2 or RXR. The antagonist behavior of RAR1 towards the RAR RARE may explain why in certain cell types such as keratinocytes, RAR is neither expressed nor induced by RA.Abbreviations DMEM
Dulbecco's modified Eagle medium
- DMSO
dimethyl sulfoxide
- FCS
fetal calf serum
- MEM
minimal Eagle medium
- NHK
normal human keratinocyte
- RA
retinoic acid
- RAR
retinoic acid receptor
- RARE
retinoic acid responsive element
- TRE
thyroid responsive element
- VDRE
vitamin D response element
- RXR
retinoid X receptor 相似文献
7.
Horn's model is generalized to state that the optimal pattern of distribution for foragers will correlate with the degree of resource patchiness; in particular (1) where resource attributes are less patchy, the optimal distribution for foragers is to be dispersed, and (2) where resource attributes are more patchy, the optimal distribution for foragers is to be aggregated. Optimality is assessed as the minimum round-trip distance from the forager's home base to a resource item. Patchiness is assessed according to the state taken by any of four resource attributes: dispersion (in space), supply (in time), particle size, and lasting properties. Horn's original contrast between (1) stable and evenly dispersed resources, and (2) mobile and clumped resources is shown to have been internally contradictory; that is, the optimal distribution for foragers would have been the same in both cases. 相似文献
8.
A new -glucosidase was partially purified from Trichoderma viride cellulase. This -glucosidase catalyzed a transglycosylation reaction of cellobiose to give -D-Glc-(16)--D-Glc-(14)-D-Glc (1, yield: 18.8%) and -D-Glc-(16)--D-Glc-(16)--D-Glc-(14)-D-Glc (2, 3.7%), regioselectively. Furthermore, the enzyme regioselectively converted laminaribiose and gentiobiose into -D-Glc-(16)--D-Glc-(13)-D-Glc (3, 15.3%) and -D-Glc-(16)--D-Glc-(16)-D-Glc (4, 20.2%), respectively. The structures (1–4) of the products were determined by 1H and 13C NMR spectroscopies. This high regio- and stereoselectively of the -glucosidase could be applied for oligosaccharide synthesis. 相似文献
9.
Jagroop S. Dahiya 《Plant and Soil》1991,134(2):297-304
A broad-host-range plasmid (pEA2-21) containing a Bradyrhizobium sp (F-4) nod DABC-lacZ translation fusion was constructed and used to monitor nod gene expression in response to pigeonpea root exudate. Two nod-inducing compounds were isolated and identified. Spectral analysis using ultraviolet absorption, infrared spectra, proton nuclear magnetic resonance, and mass spectrometry showed that the two inducers were 5,4-dihydroxy-6-(3-methyl-2-butenyl)-2, 2-dimethyl pyrano-[5, 6:7, 8]-flavanone (cajaflavanone) and 2,4,5-trihydroxy-5-isopentenyl-6, 7-dimethylchromene iso-flavanone (cajanone). When pEA2-21 was introduced into Rhizobium trifolii and R. meliloti cajanone and cajaflavanone did not induce nod gene indicating that specificity of induction appears to be influenced by the host-strain genome. 相似文献
10.
Summary The B factors of Schizophyllum commune are of 3 classes: The high recombining class I has 7 alleles and 7 alleles; the low recombining classes are class II with 7 allels and probably 2 alleles and class III with probably 2 (or also 2) alleles and 7 allels. A fourth hypothetical class (-) was not found and either does not exist or is indistinguishable from class III by the tests employed. The and alleles differ from and by either (a) mutations affecting both mating specificity and recombination frequency, or (b) deletions involving most of the B region.The research was supported by a grant from the Atomic Energy Commission of the U.S. No. (30-1)-3875 and was performed at the Biological Laboratories, Harvard University, Cambridge, Mass., U.S.A. 相似文献
11.
The replication of chromosomal DNA in human and Chinese hamster cell populations has been studied by means of the DNA fiber autoradiography. It was found that the rate of DNA replication for one fork in human cells varies from 0.2 to 0.9 m/min, the average being 0.6 m/min. In the Chinese hamster cells the rate of DNA replication is greater, varying from 0.3 to 1.2 m/min, the average being 0.8 m/min. There are no clusters containing a great number of replication units in human and Chinese hamster cells. Sequences consisting of two or three replicons which belong to single DNA molecule have been observed, but their frequency was relatively low. The distances between the initiation points in such sequences of replicons vary from 40 to 280 m, the average value being 130 m. This value represents the minimum size of the replication units which have completed the DNA synthesis within 3 h of the S-period. The DNA synthesis in most replication units fails to be accomplished within the three hours of labelling. The process can be completed only in the fragments of DNA molecules of 40 to 200 m (the average value being 100 m) in human cells, whereas in the Chinese hamster cells the fragments of 40 to 250 m (the average being about 140 m) are completely replicated. Provided that the replication is bidirectional the complete replicons are supposed to contain two such fragments. Consequently, the greater part of replication units in mammalian cells covers the pieces of a few hundred microns in DNA molecules. The relation between replication process at the DNA molecules level and that at the metaphase chromosome level is discussed. 相似文献
12.
Robert F. Troxler Gwynneth D. Offner Jen-Wei Jiang Bai-Lin Wu James C. Skare Aubrey Milunsky Herman E. Wyandt 《Human genetics》1993,92(6):563-566
Among 639 spontaneous abortions between the 8th and 14th week of gestation 342 (53.5%) revealed an abnormal karyotype. While the rate of trisomies distinctly increased with advancing maternal age, a decrease in the rate of 45,X conceptuses and polyploidies was observed among abortions from older women. The overall relation of XXXXXXYY among the tetraploidies was 1411 and that of XXXXXYXYY among the triploidies was 26 361. However, when the latter was related to maternal age, a reversal of the XXXXXY ratio of 12 in the younger to 21 in the older age groups became evident. Furthermore a decrease in the rate of paternally derived partial hydatidiform moles was found among the triploid abortion specimens from older women. From these observations we conclude that digyny plays a major role in the origin of triploidy in the increased maternal age groups, while diandry related to immaturity of oocytes and impairment of oocyte cortical function is more frequent in triploid abortions from younger women. 相似文献
13.
Henrik Saxe 《Trees - Structure and Function》1993,8(1):39-48
Summary Analysis of 62 mature Norway spruce (Picea abies provenance Viborg) trees growing in a Danish plantation was undertaken along with analysis of their nutrient contents (N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B and Na), in each of the three youngest needle age classes, from branches of four exposure directions near the tree top. The aim was to investigate if one among the studied possible predisposing factors was also a triggering factor in the 1989 outbreak of the Red Norway spruce decline in Denmark. Neither nutrient imbalance or deficiency, nor excessive N-deposition or salt-stress were indicated as triggering factors in 1989. The Red syndrome, noticeable for the bright red colour of the current-year needles, was found to be an extension of the European type Novel Decline. Red syndrome is similar to previously reported phenomena of top-dying and sub top-dying, in that it had fewer needle age classes and significantly higher contents of mobile cations (and Ca) in the younger needle classes. Tree ring analysis suggested that the Red syndrome was initiated in the early 1980s, when the trees experienced adverse climatic conditions. Because of this long-term development of the Red Norway spruce decline syndrome, it is concluded that a triggering factor is of minor importance relative to the multitude of predisposing factors. 相似文献
14.
Boel Lanne Jeana Cîopraga Jörgen Bergström Cecilia Motas Karl-Anders Karlsson 《Glycoconjugate journal》1994,11(4):292-298
The carbohydrate-binding specificity ofPseudomonas aeruginosa lectin I (PA-I) in iodinated or biotinylated form was studied. A large number of glycosphingolipids, as well as some glycoproteins and neoglycoproteins were used as ligands. Also, inhibition by free saccharides of PA-I binding to glycosphingolipids was tested. It was found that the lectin binds most strongly to terminal and nonsubstituted Gal3Gal- or Gal4Gal-structures.Abbreviations PA-I
Pseudomonas aeruginosa lectin I
- Cer
ceramide
- lactosylceramide
Gal4GlcCer
- iso globotriaosylcerami
Gal3Gal4GlcCer
- globotriaosylceramide
Gal4Gal4GlcCer
- globoside or globotetraosylceramide
GalNAc3Gal4Gal4GlcCer
- Forssman glycolipid
GalNAc3GalNAc3Gal4Gal4GlcCer
- P1 glycolipid
Gal4Gal4GlcNAc3Gal4GlcCer
- lactoneotetraosylceramide
Gal4GlcNAc3Gal4GlcCer
- B5 glycolipid
Gal3Gal4GlcNAc3Gal4GlcCer
- gangliotetraosylceramide
Gal3GalNAc4Gal4GlcCer
- GM1
Gal3GalNAc4(NeuAc3)Gal4GlcCer
- RBC
red blood cells
- BSA
bovine serum albumin
- PBS
phosphate-buffered saline
- SDS
sodium dodecyl sulfate
- TLC
thin-layer chromatography
- HPLC
high pressure liquid chromatography
- MS
mass spectrometry
- FAB
fast-atom bombardment
- EI
electron impact 相似文献
15.
Effie W. Petersdorf Robert L. Griffith Henry A. Erlich Eric M. Mickelson Anajane G. Smith Brenda B. Nisperos Paul J. Martin John A. Hansen 《Immunogenetics》1990,32(2):96-103
We have used restriction fragment length polymorphism (RFLP) analysis and DNA sequencing to characterize two distinct DRB1 alleles expressed on DRw52 and DQw7-associated haplotypes but not readily defined by conventional DR serology. These two haplotypes, designated HLA-D HAG and PEV, react variably with DRw13(w6), DRw14(w6), and the more broad DR 3+6 antisera. Analysis of RFLP revealed that HLA-D HAG and PEV are associated with different DRw52 variants, and that HAG is indistinguishable from DRw18(3) haplotypes. Sequencing of the HAG and PEV DRB1 genes showed each to represent novel alleles. Nevertheless, these sequences show similarities with the other alleles of the DR5, w6, and w8 family. HAG (DRB1*1303) appears to have arisen either from two recombinational events involving at least three DRB1 sequences (DRB1*1101, DRB1*0803, DRB1*0401) or from a single recombinational event together with multiple point mutational events. PEV appears to represent a DRB1*1301-1302/DRB1*1101 recombinant allele, with recombination having occured in the region of bases 175 – 198. The results of this study suggest that the DRw52 family haplotypes is derived from a relatively restricted number of ancestral sequences, with diversity among DRB1 alleles within this family arising through gene conversion or recombination events. 相似文献
16.
Does “ring syndrome” exist? An analysis of 207 case reports on patients with a ring autosome 总被引:8,自引:3,他引:5
György Kosztolányi 《Human genetics》1987,75(2):174-179
Summary Analysis of 207 case reports on patients with ring autosome showed that: (1) Forty patients, a fifth of the total, had extreme growth failure together with an otherwise almost-normal appearance, viz. no major malformation, no specific deletion syndrome, no or only a few unspecific minor anomalies. This phenotype may be regarded as the ring syndrome, a term proposed by Cote et al. (1981) since it is independent of what chromosome is involved. (2) Severe growth failure, the sole major physical abnormality in the ring syndrome, was seen significantly more often among patients with ring of larger chromosomes than among patients with a smaller ring, indicating that the greater the chromosome involved in ring formation, the higher is the probability of severe growth failure. (3) Larger ring chromosomes showed significantly more often instability than smaller rings, suggesting that there may be a correlation between ring instability and the size of the chromosome involved. (4) Growth failure was present in significantly more patients with a labile ring than with a stable ring, indicating that a correlation may exist between ring instability and growth failure. It is suggested that the ring syndrome observed in many cases with ring autosome may result from end-to-end fusion of chromosome ends, an event not involving deletion in the genetic sense. It is also suggested that the ring syndrome is caused by a continuous generation of secondary aneuploid cells with increased mortality, i.e. structural ring instability which seems to be a function of the size of the chromosome involved. Thus, formation of a ring chromosome in certain cases might be regarded as a structural mutation, i.e. an alteration in the structure of the genetic material per se, rather than a loss or gain of genetic dosages. 相似文献
17.
Kurt G. I. Nilsson 《Biotechnology letters》1996,18(7):791-794
A new approach for the highly specific preparation of L-serine conjugates of lactosamine and Gal1-3GalNAc is described. Thus, the L-serine derivative of lactosamine Gal1-4GlcNAc-O-(N-Z)-Ser-OEt, was obtained from lactose, employing GlcNAc-O-(N-Z)-Ser-OEt as acceptor and a yeast -galactosidase as catalyst Galp 1-3GalNAc-O-(N-Alloc)-Ser-OMe was obtained from lactose, employing GalNAc-O-(N-Alloc)-Ser-OMe as acceptor and -galactosidase from bovine testes as catalyst. 相似文献
18.
Hubert Felle 《Planta》1981,152(6):505-512
In the aquatic liverwort Riccia fluitans, membrane depolarization (m), change in membrane conductance (gm), and current-voltage (I-V) characteristics in the presence of different amino acids as well as the uptake of 14C-labeled amino acids were measured. L-isomers of the tested amino acids generate larger electrical effects (m, gm) than D-isomers, and the I-V characteristics show that the positive electrical inward-current of 20 mA m-2 generated by 0.5 mM D-serine is only about 50% of the current generated by adding 0.5 mM L-serine. Whereas - and -amino acids rapidly depolarize the membrane to the same extend, with -aminobutyric acid (-AB) and dipeptides no significant electrical effects have been measured. The uptake kinetics of 14C-labeled amino acids display three components: (I) A saturable high-affinity component with Ks-values of 48 M D-alanine, 12 M -aminoisobutyric acid (AIB), 9 M L-alanine, 8 M L-proline, and 6 M L-serine, respectively; (2) an apparently linear low-affinity component, and (3) an also linear but unspecific component at concentrations >20 times the given Ks-value. Uptake of 14C-labeled AIB can be inhibited competitively by all tested neutral amino acids, the L-isomers being more effective than the D-isomers, as well as by ammonium or methylamine. Vice versa, AIB competitively inhibits uptake of L-serine and L-alanine. It is concluded that an uncharged stereospecific carrier for the investigated amino acids exists in the plasmalemma of Riccia fluitans. Accumulation ratios of about 50 suggest secondary active transport driven by a transmembrane electro-chemical gradient (mainly m) which is generated by the electrogenic proton pump. It is suggested that this carrier binds to the amino group forming either a charged binary complex with positively charged amines (Felle 1980), or an uncharged complex with -AB or dipeptides, whereas electrogenic transport of - and -amino acids is mediated by a ternary carrier complex, probably charged by a proton.Symbols and Abbreviations m
membrane potential (mV)
- Eco
equilibrium potential (mV) of the transport system
- gm
membrane (slope) conductance (Sm-2)
- gm
change in gm
- I-V curve
current-voltage curve
- AIB
-aminoisobutytric acid
- -AB
-aminobutyric acid 相似文献
19.
Christakopoulos P. Mamma D. Kekos D. Macris B.J. 《World journal of microbiology & biotechnology》1999,15(4):443-446
Production of acetyl esterase (EC 3.1.1.6) by Fusarium oxysporum strain F3 was enhanced by optimization of growth conditions. Under optimal conditions, activities as high as 0.89U/ml of culture medium were obtained. The culture filtrate was equally active on p-nitrophenyl acetate and acetylxylan. The enzyme produced 71% deacetylation of acetylxylan in 2h at 40C. Activity was optimized at pH6.5 and at 55C. The respective Km values for p-nitrophenyl acetate and acetylxylan were 0.25mM and 1.05% (w/v) and the Vm values were 0.65 and 0.43mol acetate/min/mg protein. 相似文献
20.
Abdulrahman M. Al Senaidy 《Molecular and cellular biochemistry》1996,154(1):71-75
Plasma - and -tocopherol were monitored in pregnant women throughout healthy gestational periods and after delivery and were compared with that of non pregnant women. The mean plasma -tocopherol and -tocopherol concentrations in non pregnant Saudi women (15.2 ± 1.3 and 1.8 ± 0.2 ol/l respectively) were found within normal range. The maternal plasma -tocopherol level steadily increased reaching maximum level (19.1 ± 1.6 mol/l) at late gestation and then gradually decreased after delivery. On the contrary, the optimum level of -tocopherol (2.1 ± 0.2 mol/l) was at mid gestation, followed by a progressive decrease until one month after delivery (1.5 ± 0.1 ol/l). This study shows that the maternal plasma - and -tocopherol have different profiles that may be attributed to their different responses to the changes in maternal lipids during pregnancy. 相似文献