Double nuclei

The most distant of the three objects (D = 100 Mpc), NGC 6240 exhibits a double nuclei in radio and visible and a very strong H2 peak between the nuclei indicating a shock at the interface of the colliding galaxies. The 3.3 pm image is dose to the radio or [Fe H] maps and confirms that both nudei are star-forming. The Line/Continuum map (Fig. 3) shows i) depletion of PAH at both peaks i) depletion of PAH at ESE perpendicular to the nudeus-nudeus axis exactly where a superwind was evidenced (Heckman, Armus Miley, 1990) Hi) a maximum at WSW, where CO emission peaks (Wang, ScoviUe Sanders, 1991). 

The shielding at a given nucleus arises from the virtually instantaneous response of the nearby electrons to the magnetic field. It therefore fluctuates rapidly as the molecule rotates, vibrates and interacts with solvent molecules. The changes of shift widi rotation can be large, particularly when double bonds are present. For... 

The helium atom is similar to the hydrogen atom with the critical difference that there are two electrons moving in the potential field of a nucleus with a double positive charge (Z = 2) (Eig. 8-1). 

Section 28 9 Within the cell nucleus double helical DNA adopts a supercoiled terti ary structure m which short sections are wound around proteins called histones This reduces the effective length of the DNA and maintains it m an ordered arrangement... 

Although the natural abundance of nitrogen-15 [14390-96-6] leads to lower sensitivity than for carbon-13, this nucleus has attracted considerable interest in the area of polypeptide and protein stmcture deterrnination. Uniform enrichment of is achieved by growing protein synthesi2ing cells in media where is the only nitrogen source. reverse shift correlation via double quantum coherence permits the... 

The compounds of this article, ie, ftve-membered heterocycles containing two adjacent nitrogen atoms, can best be discussed according to the number of double bonds present. Pyrazoles contain two double bonds within the nucleus, imparting an aromatic character to these molecules. They are stable compounds and can display the isomeric forms, (1) and (2), when properly substituted. Pyrazoles are scarce ia nature when compared to the imidazoles (3), which are widespread and have a central role ia many biological processes. 

Pyrazolines have only one double bond within the nucleus and, depending on the position of the double bond, can exist ia three separate forms l-pyrazoliue [2721 3-9] (6), 2-pyrazoliae [109-98-8] (7), and 3-pyrazoliae [6569-23-9] (8). 

An interesting variant in which nucleophilic aromatic substitution is carried out on the crown nucleus rather than using the crown as nucleophile was reported by Haines . In this approach, hexafluorobenzene was stirred in 1,2-dimethoxyethane at room temperature with pentaethylene glycol and sodium hydride. A double nucleophilic aromatic substitution occurred affording 2, 3, 4 ,5 -tetrafluorobenzo-15-crown-5 as an oil in 38% yield. The reaction is illustrated below. 

The assumption of these conjugated double bonds makes possible a tetracyclic nucleus which accords with the suggestion previously made by the authors that these alkaloids might be structurally related to the diterpenes. It may also be noted that one of the nitric acid oxidation products of pseudaconitine has been recorded as unexpectedly giving a pyrrole reaction on destructive distillation. ... 

The presence of functional groups on the steroid nucleus can affect the course of the epoxidation reaction thus epoxidation of 3/ -chlorocholest-4-ene (11) gives the 4a,5a-epoxide in 97 % yield, whereas the 3a-chloro group hinders (presumably sterically) attack on the 4,5-double bond towards the a-face of the molecule. The 3a-acetoxy function similarly influences the selectivity of the epoxidation of cholest-4-enes, a 53 47 mixture of the respective 4 , 5a- and 4jS, 5jS-epoxides being obtained after exposure of the 3a-acetoxy-4-ene (13) to perbenzoic acid. 

Many selective epoxidations are possible with polyunsaturated steroids. In general, oc, -unsaturated ketones are not attacked by peracid, although linear dienones react slowly at the y,5-double bond. Aw-Chloroperbenzoic acid is the reagent of choice for this reaction.When two isolated double bonds are present in the steroid nucleus, e.g. (27) and (30), the most highly substituted double bond reacts preferentially with the peracid. Selective epoxidation of the nuclear double bond of stigmasterol can likewise be achieved.However, one exception to this general rule has been reported [See (33) (34)]. ... 

In analogy with the peracid attack on steroidal double bonds, the formation of the bromonium ion, e.g., (81a), occurs from the less hindered side (usually the a-side of the steroid nucleus) to give in the case of the olefin (81) the 9a-bromo-l l -ol (82). Base treatment of (82) provides the 9 5,1 l S-oxide (83). Similarly, reaction of 17/3-hydroxyestr-5(10)-en-3-one (9) with A -bromosuccinimide-perchloric acid followed by treatment with sodium hydroxide and sodium borohydride furnishes the 3, 17 5-dihydroxy-5a,l0a-oxirane. As mentioned previously, epoxidation of (9) with MPA gives the 5, 10 -oxirane. °... 

Nucleus The nucleus is separated from the cytosol by a double membrane, the nuclear envelope. The DNA is complexed with basic proteins (histones) to form chromatin fibers, the material from which chromosomes are made. A distinct RNA-rich region, the nucleolus, is the site of ribosome assembly. The nucleus is the repository of genetic information encoded in DNA and organized into chromosomes. During mitosis, the chromosomes are replicated and transmitted to the daughter cells. The genetic information of DNA is transcribed into RNA in the nucleus and passes into the cytosol where it is translated into protein by ribosomes. 

Introduction of an additional double bond into the tricyclic nucleus, on the other hand, is consistent with antidepressant activity. Alkylation of the potassium salt, obtained on treatment of hydrocarbon, 38, with ammonia, with the chlorocarbamate, 39, affords the intermediate, 40. Basic hydrolysis leads to protrip-tylene (41). ... 

He suggested a nomenclature for the terpenes by which those compounds which contain a double linkage between the nucleus and the side chain should be called pseudo-compounds, whilst the compounds with the double linkage in the nucleus should be the ortho-compounds. He suggested the following formulae —... 

Semmler deduces from these results that natural selinene is composed of a mixture containing principally the hemicyclic pseudo-(yS)-selinene, together with a small quantity of ortho-(a)-selinene. By passing through the dihydrochloride it is possible to convert the pseudo-(y8)-selinene into the ortho-(a)-selinene or regenerated selinene, which contains only a. small proportion of the (3 form. Both yield the same solid dihydrochloride. Selinene affords a typical example of the possibility of the displacement of the double bond from the side chain into the nucleus. 

Sadtler concluded finally that double bonds seem to aid in bringing about reaction when close to the. CHO group, e.g., citral, cinnamic aldehyde, and that proximity of the benzene nucleus to the. CHO group, as. in the case of benzaldehyde and vanillin, was also probably a factor, while the only active ketones were those containing double bonds near to the. CO group. 

E Transcription is the process by which RNA is produced to carry genetic information from the nucleus to the ribosomes. A short segment of the DNA double helix unwinds, and complementary ribonucleotides line up to pro-... 

Transcription (Section 28.4) The process by which the genetic information encoded in DNA is read and used to synthesize RNA in the nucleus of the cell. A smal I portion of double-stranded DNA uncoils, and complementary ribonucleotides line up in the correct sequence for RNA synthesis. 

Although there are many potential places around the steroid nucleus where desaturation may occur, only a few are of commercial value. The most important is the introduction of a second double bond in ring A already containing a double bond at position 4. Thus ... 

In an acid (pH less than 3), the acid donates a hydrogen nucleus, and the molecule becomes positive. The bond next to the oxygen becomes a double bond, and the molecule now absorbs green light, so it appears red. 

The secular equation for 1,2-dihydroanthracene resulting from the consideration of (I) the symmetrical unexcited structure, (II) the two unsymmetrical unexcited structures, (III) the sixteen first-excited structures not involving conjugation of the double bond and the naphthalene nucleus, and (IV) the six first-excited structures involving this conjugation, is... 

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