共查询到20条相似文献,搜索用时 15 毫秒
1.
Robert Rosen 《Bulletin of mathematical biology》1965,27(1):11-14
The present note consists of two separate but related parts. In the first, a new graphtheoretic proof is presented that an
(ℳ,R)-system must always contain a nonreestablishable component. The second considers some questions concerning the relation between
re-establishability and the time-lag structure in (ℳ,R)-systems. It is supposed that the reader is familiar with the terminology of the author's previous work on (ℳ,R)-systems, particularly R. Rosen,Bull. Math. Biophysics,20, 245–260, 1958. 相似文献
2.
N. Rashevsky 《Bulletin of mathematical biology》1960,22(1):73-84
The principle of biotopological mapping (Rashevsky, 1954,Bull. Math. Biophysics,16, 317–48) is given a generalized formulation, as the principle of relational epimorphism in biology. The connection between
this principle and Robert Rosen’s representation of organisms by means of categories (1958,Bull. Math. Biophysics,20, 317–41) is studied. Rosen’s theory of (M,R)-systems, (1958,Bull. Math. Biophysics,20, 245–60) is generalized by dropping the assumption that only terminalM
i
components are sending inputs into theR
i
components. It is shown that, if the primordial organism is an (M,R)-system, then the higher organisms, obtained by a construction well discussed previously (1958,Bull. Math. Biophysics,20, 71–93), are also (M,R)-systems. Several theorems about such derived (M,R)-systems are demonstrated.
It is shown that Rosen’s concept of an organism as a set of mappings throws light on phenomena of synesthesia and also leads
to the conclusion that Gestalt phenomena must occur not only in the fields of visual and auditory perception but in perceptions
of any modality. 相似文献
3.
Robert Rosen 《Bulletin of mathematical biology》1959,21(2):109-128
The general Theory of Categories is applied to the study of the (M, R)-systems previously defined. A set of axioms is provided which characterize “abstract (M, R)-systems”, defined in terms of the Theory of Categories. It is shown that the replication of the repair components of these
systems may be accounted for in a natural way within this framework, thereby obviating the need for anad hoc postulation of a replication mechanism.
A time-lag structure is introduced into these abstract (M, R)-systems. In order to apply this structure to a discussion of the “morphology” of these systems, it is necessary to make
certain assumptions which relate the morphology to the time lags. By so doing, a system of abstract biology is in effect constructed.
In particular, a formulation of a general Principle of Optimal Design is proposed for these systems. It is shown under what
conditions the repair mechanism of the system will be localized into a spherical region, suggestive of the nuclear arrangements
in cells. The possibility of placing an abstract (M, R)-system into optimal form in more than one way is then investigated, and a necessary and sufficient condition for this occurrence
is obtained. Some further implications of the above assumptions are then discussed. 相似文献
4.
N. Rashevsky 《Bulletin of mathematical biology》1971,33(4):555-559
In combining the author's theories of organismic sets (Rashevsky,Bull. Math. Biophysics,31, 159–198, 1969a) and Robert Rosen's theory of (M, R)-systems (Bull. Math. Biophysics,20, 245–265, 1958), a conclusion is reached that the number of either normal or pathological phenomena in organismic sets may
occur. Those phenomena are characterized by occurring spontaneously once in a while but are not exactly periodic. Some epilepsies
are an example of such pathological phenomena in the brain. 相似文献
5.
Lloyd A. Demetrius 《Bulletin of mathematical biology》1966,28(2):153-160
Rosen’s identification of abstract biological systems, called (M,R)-systems, with sequential machines is formally characterized. It is then shown that the determination of environmental alterations
of (M,R)-systems from a knowledge of the response sequence and the structure of the system, which we call behavioral reversibility,
can be interpreted as information-losslessness of sequential machines. Applying this relationship, necessary conditions for
behavioral reversibility are derived. It is further shown that, similar to Rosen’s work on structural reversibility, (M,R)-systems are behaviorally reversible only if the number of physically realizable mappings are restricted. 相似文献
6.
Michael Abib 《Bulletin of mathematical biology》1966,28(4):511-517
We show that when we represent (ℓ, ℛ)-systems with fixed genome as automata (sequential machines), we get automata with output-dependent
states. This yields a short proof that ((ℓ, ℛ)-systems from a subcategory of automata—and with more homomorphisms than previously
exhibited. We show how ((ℓ, ℛ)-systems with variable genetic structure may be represented as automata and use this embedding
to set up a larger subcategory of the category of automata. An analogy with dynamical systems is briefly discussed. This paper
presents a formal exploration and extension of some of the ideas presented by Rosen (Bull. Math. Biophyss,26, 103–111, 1964;28, 141–148;28 149–151). We refer the reader to these papers, and references cited therein, for a discussion of the relevance of this material
to relational biology. 相似文献
7.
Bellila A Tremblay C Pichette A Marzouk B Mshvildadze V Lavoie S Legault J 《Phytochemistry》2011,72(16):2031-2036
Withanolide-type steroids, withametelin Q (1) and 12α-hydroxydaturametelin B (2) along with three known withanolides, were isolated from leaves of Datura metel L. (Solanaceae). The respective structures, characterized mainly by NMR spectroscopy, were identified as (20R,22R,24R)-21,24-epoxy-1α,3β-dihydroxywitha-5,25(27)-dienolide-3-O-β-d-glucopyranoside (1) and (20R,22R,24R)-12α,21,27-trihydroxy-1-oxowitha-2,5,24-trienolide-27-O-β-d-glucopyranoside (2). The cytotoxicity of isolated compounds was evaluated against human lung carcinoma cells (A549) and human colorectal adenocarcinoma cells (DLD-1), respectively. Compound 2 exhibited cytotoxicity against A549 and DLD-1 cell lines, with IC50 values of 7 and 2.0 μM, respectively. However, for compounds 6 and 7, cytotoxicities were higher against DLD-1 cells with IC50 values of 0.6 and 0.7 μM. Both compounds blocked the cell cycle in the S-phase and induced apoptosis. 相似文献
8.
Tuti Wukirsari Hisashi Nishiwaki Kosuke Nishi Takuya Sugahara Koichi Akiyama Taro Kishida 《Bioscience, biotechnology, and biochemistry》2016,80(4):669-675
We compared the cytotoxic activities of dietary epoxylignans and their stereoisomers and found (?)-verrucosin, which is (7S,7′R,8R,8′R)-7,7′-epoxylignan, to be the most cytotoxic epoxylignan against HeLa cells (IC50 = 6.6 μM). On the other hand, the activity was about a factor of 10 less against HL-60. In this research on the relationship between the structure and cytotoxic activity of (?)-verrucosin 13, the 7-(4-methoxyphenyl)-7′-(3,4-dimethoxyphenyl) derivative 60, for which the activity (IC50 = 2.4 μM) is three times greater than (?)-verrucosin 13, was discovered. The induction of apoptosis by caspase 3/7 was observed upon treatment with the (?)-verrucosin derivative. 相似文献
9.
Ion C. Baianu 《Bulletin of mathematical biology》1980,42(3):431-446
The mathematical structures underlying the theories of organismic sets, (M, R)-systems and molecular sets are shown to be transformed naturally within the theory of categories and functors. Their natural
transformations allow the comparison of distinct entities, as well as the modelling of dynamics in “organismic” structures. 相似文献
10.
《Bioscience, biotechnology, and biochemistry》2013,77(10):2367-2374
Synthetic studies of annonaceous acetogenins starting from (?)-muricatacin (1a) or (+)-muricatacin are described, involving (?)-muricatacin (1a), mono-THF acetogenin, solamin (2), reticulatacin (3), (15R, 16R, 19S, 20S)-cis-solamin (4a) and (15S, 16S, 19R, 20R)-cis-solamin (4b), non-adjacent bis-THF acetogenin, 4-deoxygigantecin (5), and epoxide-bearing acetogenin, (15S, 16R, 19S, 20R)-diepomuricanin (6a). 相似文献
11.
Choong Je Ma Young Choong Kim 《Journal of enzyme inhibition and medicinal chemistry》2013,28(5):1117-1121
The dichloromethane fraction of the bark of Machilus thunbergii Sieb. et Zucc. (Lauraceae) significantly protected primary cultures of rat cortical cells exposed to the excitotoxic amino acid, L-glutamate. Through the activity-guided isolation from the CH2Cl2 fraction, (+)-9′-hydroxygalbelgin (1), isogalcatin B (2), (7S,8S,8′R)-3′,4′-dimethoxy-3,4,-methylenedioxylignan-7-ol (3), 1-hydroxy-7-hydroxymethyl-6-methoxyxanthone (4), 5,7-dimethoxy-3′,4′-methylenedioxyflavan-3-ol (5), (+)-(3S,4S,6R)-3,6-dihydroxypiperitone (6), protocatechuic acid methyl ester (7) and tyrosol (8) were obtained. All of them had significant neuroprotective activities against glutamate-induced neurotoxicity in primary cultures of rat cortical cells at concentrations ranging from 0.1 μM to 10.0 μM and were comparable to MK-801, a well-known inhibitor of glutamate receptor. 相似文献
12.
Robert Rosen 《Bulletin of mathematical biology》1966,28(2):149-151
The condition which allows the existence of induced replication maps in (M,R)-systems is shown to place strong restrictions on the “richness” of the category from which these systems can be constructed.
This condition also admits of a simple biological interpretation, which can be checked empirically, and which may offer insight
into the physical and biological realizations of these abstract systems. 相似文献
13.
Suspension cultured cells of Caragana chamlagu (Leguminosae) converted zerumbone (1) into zerumbone epoxide (2) as the intermediate, (2R,3R,7R)-2,3-epoxy-9-humulen-8-one (3) and (2R,3S,7R)-2,3-epoxy-9-humulen-8-one (4) as new sesquiterpenes in 11%, 36% and 21% yields, respectively. 相似文献
14.
为了解柯拉斯那(Aquilaria crassna)的化学成分,从其所产沉香中分离得到10个化合物,经波谱分析分别鉴定为:6,8-羟基-2-(2-苯乙基)色酮(1),6,8-二羟基-2-[2-(4-甲氧基苯)乙基]色酮(2),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-5-(2-phenylethyl)-7H-oxireno[f][1]benzopyran-7-one(3),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-[2-(4-methoxyphenyl)-ethyl]-7H-oxireno[f][1]benzopyran-7-one(4),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-5-[2-(3-hydroxy-4-methoxyphenyl)-ethyl]-7H-oxireno[f][1]benzopyran-7-one(5),oxidoagarochromone B(6),oxidoagarochromone C(7),(5S,6R,7S,8R)-2-[2-(3′-hydroxy-4′-methoxyphenyl)ethyl]-5,6,7,8-tetrahydroxy-5,6,7,8-tetrahydrochromone(8),6,7-cis-dihydroxy-2-(2-phenylethyl)-5,6,7,8-tetrahydrochromone(9),N-trans-feruloyltyramine(10)。化合物3~5和8~10为首次从柯拉斯那沉香中分离得到。化合物1,3,6,7,9和10对乙酰胆碱酯酶具有一定的抑制活性,化合物4对人慢性髓原白血病细胞株K-562和人胃癌细胞株SGC-7901均具有较小的抑制作用,化合物1和3对人肝癌细胞株BEL-7402也有抑制活性。 相似文献
15.
(2S,3R,1′S,2′S)-Serricorole (1) and (2S,3R,1′R)-serricorone (2), sex pheromone components of the cigarette beetle (Lasioderma serricorne F.), were synthesized, starting from the enantiomers of methyl 3-hydroxypentanoate. The stereochemistry of the naturally occurring 1 was determined to be 2S,3R,1′S,2′S, and that of 2 to be 2S,3R,1′RS by comparing between the CD spectra of the natural and synthetic samples. 相似文献
16.
17.
Masakazu Aburatani Tadashi Takeuchi Kenji Mori 《Bioscience, biotechnology, and biochemistry》2013,77(12):3043-3047
(22R,23R,24S)-22,23-Isopropylidenedioxy-5α-ergost-2-en-6-one 2b is an important intermediate of brassinolide. We found that the enone 2b can be prepared by transformation of (22R,23R,24S)-3α,5-cyclo-22,23-isopropylidenedioxy-5α-ergostan-6-one 5b with catalytic amount of both p-TsOH and NaBr in DMF under reflux. 5b was prepared from (22R,23R,24S)-3α,5-cyclo-22,23-dihydroxy-6β-methoxy-5α-ergostane 9b or a 6β-benzyloxy compound 9c, which was obtained in a manner similar to Mori’s brassinolide synthesis. The enone 2b was eventually prepared via a benzyl ether 9c from stigmasterol 3a in a 15.5% yield in 11 steps. 相似文献
18.
Sachio Kudo Takayuki Oritani Kyohei Yamashita 《Bioscience, biotechnology, and biochemistry》2013,77(9):2315-2319
Optically active tiraras-cycloheximide isomers such as cycloheximide [(2S,4S,6R,αR)-form (1)], naramycin B[(25,4S,6RαR)-form(4)], and new stereoisomers (2S,4S,6S,αS)-form (8) and (2S,4S,6R,αS)-from (9) were synthesized by an aldol condensation of trans-2,4-dimethyl-l-cyclohexanone (5b), with 4-(2-oxoethyl)-2,6-piperidinedione(6). The antimicrobial activity of trans- cycloheximide isomers (1, 4, 8, and 9) was examined against S. cerevisiae and P. oryzae. The stereoisomers 1 and 4 exhibited marked antimicrobial activity against both microorganisms as compared with their C- α-epimers 8 and 9. 相似文献
19.
《Bioscience, biotechnology, and biochemistry》2013,77(12):2384-2389
Bacterial strain B-009, capable of using racemic 1,2-propanediol (PD), was identified as a rapid-growing member of the genus Mycobacterium. The strain is phylogenetically related to M. gilvum, but has slightly different physiological characteristics. An NAD+-dependent enantioselective alcohol dehydrogenase, which acts on R-PD, was purified from the strain. The enzyme was a homodimer of a peptide coded by a 1047-bp gene (mbd1). A highly conserved sequence for medium-chain dehydrogenase/reductases with a preference for secondary alcohols was found in the gene. Hydroxyacetone was produced from R-PD by an enzymatic reaction, indicating that position 2 of the substrate was oxidized. The enzyme activity was highest for (2R,3R)-2,3-butanediol (R,R-BD), enabling the enzyme to be identified as (2R,3R)-2,3-butanediol dehydrogenase (R,R-BD-DH). A homology search revealed M. gilvum, M. vanbaalenii, and M. semegmatis to have ORFs similar to mbd1, suggesting the widespread distribution of genes encoding R,R-BD-DH among mycobacterial strains. 相似文献
20.
Takayuki Oritani Sachio Kudo Kyohei Yamashita 《Bioscience, biotechnology, and biochemistry》2013,77(3):757-760
Asymmetric hydrolysis of acetate (10) of (±)-t-2,t-4-dimethyl-r-l-cyclohexanol with Bacillus subtilis var. niger gave (?)-(lS,2S,4S)-2,4-dimethyl-l-cyclohexanol (6a) and (+)-(1R,2R,4R)-acetate (10b) with high optical purities. Optically pure (?) and (+)-alcohols (6a and 6b) were prepared via corresponding 3,5-dinitrobenzoates. Oxidation of alcohols (6a and 6b) with chromic acid gave optically pure (?)-(2S,4S) and (+)-(2R,4R)-2,4-dimethyl-l-cyclohexanones (2a and 2b), respectively. 相似文献