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Search for "origin" in Full Text gives 345 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Glycoscience@Synchrotron: Synchrotron radiation applied to structural glycoscience
Beilstein J. Org. Chem. 2017, 13, 1145–1167, doi:10.3762/bjoc.13.114
- that bind to internal carbohydrate motifs. This is a mechanism typically found in bacterial polysaccharides. There is an occurrence of very large cavities which are open at both ends. The “side-on” entry of the antigen is often at the origin of the occurrence of conformational antigens
- complexity of starch in terms of the nature and size of its macromolecular components (amylopectin, amylose) has always been an obstacle to the elucidation of the structural components and their arrangements, which are at the origin of the birefringence of a starch granule. The structure of the crystalline
- cellular material, which indicated the occurrence of “two-dimensional’ crystals that could be further investigated by wide-angle X-ray diffraction [90]. Starch: Depending upon their botanical origin, starch granules display an elliptical shape with dimensions ranging from 0.1 to 100 µm. The advent of micro
From chemical metabolism to life: the origin of the genetic coding process
Beilstein J. Org. Chem. 2017, 13, 1119–1135, doi:10.3762/bjoc.13.111
- that envelops us. Conjectures about the origins of life do not escape this unfortunate shortcoming. Even the quest for our own origin is far from settled: There is no Adam or Eve in the origin of mankind. If you doubt, just try to work out a single-step process that would account for a change from a
- set of 48 chromosomes (their number in apes) to 46 (their number in man) in a sexed species. Starting with accidental fusion of two chromosomes, a ratchet-like continuum of changes must have distanced us from our ape ancestors. In the same way, it is implausible that there was only one origin of life
- , as unfortunately many still try to call forth. Thirty years ago, Freeman Dyson provided a convincing demonstration that, contrary to the widespread "adamist" view, which looks for a single origin to all things, there were at least two origins of life [1]. He established that before the emergence of
Aggregation behaviour of a single-chain, phenylene-modified bolalipid and its miscibility with classical phospholipids
Beilstein J. Org. Chem. 2017, 13, 995–1007, doi:10.3762/bjoc.13.99
- subtracted from the thermogram of the sample, and the DSC scans were evaluated using MicroCal Origin 8.0 software. Fourier-transform infrared spectroscopy (FTIR) Infrared spectra were collected using a Bruker Vector 22 Fourier transform spectrometer with DTGS detector operating at 2 cm−1 resolution. The
Total synthesis of TMG-chitotriomycin based on an automated electrochemical assembly of a disaccharide building block
Beilstein J. Org. Chem. 2017, 13, 919–924, doi:10.3762/bjoc.13.93
- . Proposed mechanism and origin of the selectivity. Synthesis of TMG-chitotriomycin precursor 7. Synthess of TMG-chitotriomycin (1). Synthesis of disaccharide donors. Supporting Information Supporting Information File 120: Experimental details of electrochemical glycosylation, global deprotection, and NMR
Synthesis of tetrasubstituted pyrazoles containing pyridinyl substituents
Beilstein J. Org. Chem. 2017, 13, 895–902, doi:10.3762/bjoc.13.90
- [3,4-a]quinolizin-6-ium structure 12 was established, which was confirmed by single crystal X-ray structure analysis (see Supporting Information File 1), proving also iodide as the corresponding anion [39] which acts as a leaving group in the coupling reaction and also could origin from the CuI co
Expression, purification and structural analysis of functional GABA transporter 1 using the baculovirus expression system
Beilstein J. Org. Chem. 2017, 13, 874–882, doi:10.3762/bjoc.13.88
- peptides from primary sequence databases with Mascot (http://www.matrixscience.com/). The biological function of recombinant proteins of mammalian origin expressed in insect cells may be altered by different N-glycan status. We observed that the terminal sialic acid residues are essential for the GABA
Lipids: fatty acids and derivatives, polyketides and isoprenoids
Beilstein J. Org. Chem. 2017, 13, 793–794, doi:10.3762/bjoc.13.78
- was likely a crucial process for the origin of life – and certainly still is for all existing living systems that necessarily contain lipid membranes with their interesting and finely balanced biophysical properties. In prokaryotes, these membranes define the outer surface of individual cells, while
- fundamentally different biosynthetic origin from fatty acids since they are made via terpene biosynthetic pathways. Nevertheless, steroids are highly apolar yet may contain a polar headgroup such as a 3-hydroxy function (as in lanosterol). Besides membrane formation, the highly apolar character of lipids has
Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications
Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67
- gave blue-green emission, whereas phosphoric acid-mediated CD formation gave particles with red-shifted emission profiles (Red-CD). Interestingly, Red-CDs only had stable red emission in strong acidic conditions; changing to green emission in neutral or basic pH. The origin of the tuneable fluorescence
How and why kinetics, thermodynamics, and chemistry induce the logic of biological evolution
Beilstein J. Org. Chem. 2017, 13, 665–674, doi:10.3762/bjoc.13.66
- origin of life constitutes a well-established field of research in chemical science [1] even though identifying the actual pathway by which life emerged on the early Earth will likely forever remain out of reach. The corresponding historical events left no record owing to the instability of the chemical
- hypothesis failed to eliminate the fundamental dilemma, as it led to conflicting so-called genetic and metabolic approaches to the origin of life [15]. Actually, as early as 1922, Lotka’s pioneering work, through two consecutive articles published in the same issue of PNAS and entitled “Contribution to the
- energetics of evolution” [16] and “Natural selection as a physical principle” [17], respectively, considered both approaches to the problem in order to account for the specificity of life (though the issue of the origin was not mentioned). This simple fact demonstrates how intimately bound he considered the
Conjecture and hypothesis: The importance of reality checks
Beilstein J. Org. Chem. 2017, 13, 620–624, doi:10.3762/bjoc.13.60
- alternative hypotheses as a way to advance our understanding of how life can begin on the Earth and other habitable planets. As an example of how this approach can be used, two conditions have been proposed for sites conducive to the origin of life: hydrothermal vents in salty seawater, and fresh water
- hydrothermal fields associated with volcanic landmasses. These are considered as alternative hypotheses and the accumulating weight of evidence for each site is described and analyzed. Keywords: hydrothermal fields; hydrothermal vents; origin of life; polymerization by condensation; protocells; Introduction
- thousands of scientists investigating health related research or chemistry and physics having applications in industry. Another reason is that the origin of life is best understood in interdisciplinary terms involving knowledge of astronomy, planetary science, biophysics, chemistry and biochemistry
Secondary metabolome and its defensive role in the aeolidoidean Phyllodesmium longicirrum, (Gastropoda, Heterobranchia, Nudibranchia)
Beilstein J. Org. Chem. 2017, 13, 502–519, doi:10.3762/bjoc.13.50
- carbon assignments were done according to correlations obtained in a HSQC experiment. The absence of 13C NMR resonances for sp2 hybridized carbons for C=C bonds, together with a RDE of five indicated the presence of several rings in 1, likely of steroid origin. The latter is supported by
- against omnivorous fish, it is possible that some of the numerous secondary metabolites found in this study could be useful against a wider range of predators. In summary, chemical investigation of a single large P. longicirrum specimen resulted in isolation of 19 secondary metabolites of terpenoid origin
Biosynthetic origin of butyrolactol A, an antifungal polyketide produced by a marine-derived Streptomyces
Beilstein J. Org. Chem. 2017, 13, 441–450, doi:10.3762/bjoc.13.47
- predicted as the origin of the methyl-branched three-carbon fragment (C-9/C-10/C-28). Actually, intense enhancement of the C-9 carbon signal was observed by feeding of [1-13C]propionate (Table 1). The remaining carbons not labeled by malonate-type precursors were the terminal tert-butyl carbons (C-23 to C
- -27). The origin of the tert-butyl group in polyketide biosynthesis is still unknown, however, the tert-butyl functionality of bottromycin and polytheonamide was shown to be produced by radical C-methylation of the isopropyl group of valine [31][32]. By analogy, the tert-butyl portion of 1 was most
- coding for C-methyltransferase are not present near the butyrolactol PKS genes. Further enzymatic studies are necessary to establish the order of the starter loading/C-methylation events. Conclusion In summary, we elucidated the biosynthetic origin of butyrolactol A (1) on the basis of the feeding
Adsorption of RNA on mineral surfaces and mineral precipitates
Beilstein J. Org. Chem. 2017, 13, 393–404, doi:10.3762/bjoc.13.42
- since Bernal broadly conjectured on possible roles of rocks and minerals in the assembly of complex organic species relevant to the origin of life [1]. This theme has now been revisited multiple times [2][3]. Rocks and minerals have been proposed to have had multiple roles that might have been
- catalysis, where species on the surface of the mineral stabilize a transition state with respect to adsorbed ground state species [5]. More recently, and especially after the emergence of the "RNA first" hypothesis for the origin of Darwinism on Earth [6], rocks and minerals have been considered in other
- pure mineral, the catalysis of interest can occur in defects in its crystalline surface. All of these problems are difficult to manage in a controlled laboratory environment. How are we to explore this new complexity as we accommodate those who "plead" for a role for mineralogy in models for the origin
Polyketide stereocontrol: a study in chemical biology
Beilstein J. Org. Chem. 2017, 13, 348–371, doi:10.3762/bjoc.13.39
- , attempts to illuminate the origin of the remaining centers by feeding of ethyl [2-2H2,2-13C]-succinate to produce labeled (2R)-methylmalonyl-CoA in situ, were inconclusive. Access to the erythromycin PKS (DEBS) multienzymes as pure proteins [25] allowed extender unit preference in cis-AT PKSs to be
- thus DEBS 1-TE represented an ideal system for elucidating the origin of the two configurations. In the presence of a suitable starter unit such as propionyl-CoA, (2R)-methylmalonyl-CoA as extender unit and NADPH (the cofactor for the KR domains), no product was observed. However, when (2S
- extension. Based on the presumed biosynthetic origin of these extender units (from L-serine and from a glycolytic intermediate (in all likelihood 1,3-biphospho-D-glycerate), respectively), it was initially proposed that the (2S)-isomer of aminomalonyl-ACP and the (2R)-isomers of hydroxyl-/methoxymalonyl-ACP
Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state
Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23
- phosphate buffer) [39], berberine has a significantly higher affinity (Kb = 4.2 × 105 M−1, in phosphate buffer) [40]; although both complexes are proposed to have nearly the same structure. The origin of these inconsistent data has not been assessed or discussed so far. But these observations suggest that
Organofluorine chemistry: Difluoromethylene motifs spaced 1,3 to each other imparts facial polarity to a cyclohexane ring
Beilstein J. Org. Chem. 2016, 12, 2823–2827, doi:10.3762/bjoc.12.281
- distortion is also observed for the 1,3-diaxial C–F bonds in the solid state structures of 2 [20] and 3 [21] consistent with electrostatic dipolar repulsion between these C–F bonds and indicative of the origin of the polarity of these molecules. In terms of intermolecular packing in the solid state there are
Green chemistry
Beilstein J. Org. Chem. 2016, 12, 2763–2765, doi:10.3762/bjoc.12.273
- scientific literature, the terms "green" and "sustainable" have been increasingly used and are nowadays ubiquitously present in the terminology of several research areas. The seminal origin of what is considered “green chemistry” today might be ascribed to the launch of the Responsible Care® initiative by
Effects of solvent additive on “s-shaped” curves in solution-processed small molecule solar cells
Beilstein J. Org. Chem. 2016, 12, 2543–2555, doi:10.3762/bjoc.12.249
- . Origin of the s-shape in J–V curves Despite the relatively high VOC, based on the CV data, one might expect to achieve voltages that are even higher compared with p-SIDT(FBTTh2)2, as p- SIDT(FBTThCA8)2 seems to have an even deeper HOMO level. However, a HOMO of −5.27 eV is close to the work function of
Determination of the absolute stereostructure of a cyclic azobenzene from the crystal structure of the precursor containing a heavy element
Beilstein J. Org. Chem. 2016, 12, 2211–2215, doi:10.3762/bjoc.12.212
- ; cyclic compound; enantiomer; stereostructure; X-ray crystal analysis; Introduction Chirality is a topic of fundamental importance in several branches of science [1][2][3][4][5]. Homochirality in nature was one of the most important challenges for researchers and the origin is still unsolved [6][7][8
Varioloid A, a new indolyl-6,10b-dihydro-5aH-[1]benzofuro[2,3-b]indole derivative from the marine alga-derived endophytic fungus Paecilomyces variotii EN-291
Beilstein J. Org. Chem. 2016, 12, 2012–2018, doi:10.3762/bjoc.12.188
- tentatively named as varioloid B. The NOESY spectrum indicated cis relative configuration of the two adjacent chirality centers, which was in agreement with that of 1. Given the common biosynthetic origin and congruent ECD spectrum with that of compound 1, the absolute configuration of 2 was assigned to be
Bridgehead vicinal diallylation of norbornene derivatives and extension to propellane derivatives via ring-closing metathesis
Beilstein J. Org. Chem. 2016, 12, 1877–1883, doi:10.3762/bjoc.12.177
- in Figure 2. At this point, we turned our attention to understand the configurational origin of the allyl groups in 2a. To understand whether compound 2a was formed by Claisen rearrangement (CR) of the corresponding O-allyl compound or by carbanion mediated C-allylation of the DA adduct 3a, we
Synthesis and properties of fluorescent 4′-azulenyl-functionalized 2,2′:6′,2″-terpyridines
Beilstein J. Org. Chem. 2016, 12, 1812–1825, doi:10.3762/bjoc.12.171
- origin of the fluorescence emission will be also described by time-dependent density functional theory (TDDFT) calculations. The ability of the terpyridine compounds to bind poisoning metal cations was investigated by spectrophotometric titrations of methanolic 4′-azulenyl-substituted terpyridine
- . Orbital origin of spectra The most important Kohn–Sham orbitals (ψi) playing an active role in the calculated electronic transitions are shown in Figure 6 along with their energies. The nature of the excited state(s) accessed through electronic transitions are listed in Table 4 is a contribution of
- experimental spectra. Regarding the absorption shoulder around 300 nm observed in the experimental spectrum of 4a, it was shown above that matching calculated transitions are IV, V, VI (B3LYP), IV (CAMB3LYP), and V (TPSSH). The orbital origin of these transitions is not consistent for these functionals
Experimental and theoretical insights in the alkene–arene intramolecular π-stacking interaction
Beilstein J. Org. Chem. 2016, 12, 1616–1623, doi:10.3762/bjoc.12.158
- associated to a dynamic process taking place at room temperature. In order to unravel the origin of this phenomenon, we further carried out low temperature NMR studies (Figure 3). When the CDCl3 solution of acrylate 6a was cooled gradually from 300 K the resonances corresponding to the vinylic protons
Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides
Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148
- widespread in peptidic natural products of both, non-ribosomal and post-ribosomal modified origin [5]. The biosynthetic mechanisms for heterocycle formation are numerous, and range from simple addition or condensation reactions to oxidative ring closures. The large number of mechanistically different
- [138][139]. With the exception of a few terpenoids, most tetronates are of polyketide origin, either being completely biosynthesised by a PKS or by hijacking intermediates from fatty acid biosynthesis (Figure 6). Although the larger body of tetronates is produced by Actinobacteria, they are abundant in
- organisms from different classes. Their origin often goes along with characteristic structural elements. Furylidene tetronates are for example exclusively produced by fungi and spirotetronates by Actinobacteria [139]. The biosynthetic studies that were launched since genetic information on more and more
The hydrolysis of geminal ethers: a kinetic appraisal of orthoesters and ketals
Beilstein J. Org. Chem. 2016, 12, 1467–1475, doi:10.3762/bjoc.12.143
- , consistent with proximal syn C(4/5)–H, and the geminal C(2)–OCH3 nuclei, respectively (Figure 3). The 1H NMR spectra of 11 and 14 were assigned in a similar fashion. We attribute the two-fold rate increase of 10–11 (kH+ ≈ 12 M−1 s−1) with respect to 5 (kH+ = 6.5 M−1 s−1) to be steric in origin. The
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