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Topic: Chemical conformation


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  Conformational isomerism Summary
Conformational isomerism is a form of isomerism and describes the phenomenon of molecules with the same structural formula having different chemical conformations or conformers due to atoms rotating about a bond.
N is the population of molecules in a particular conformation.
Conformational isomerism only occurs around single bonds as a result of the requirement of breaking one or more pi bonds to rotate substituents about a sigma bond axis in double and triple bonded atoms.
www.bookrags.com /Conformational_isomerism   (873 words)

  
 Chemical structure - Wikipedia, the free encyclopedia
Chemical structure refers to the spatial arrangement of atoms in a molecule and the chemical bonds that hold the atoms together.
Chemical structure can range from the very simple, such as diatomic oxygen or nitrogen molecules, to the very complex, such as protein or DNA molecules.
A common method for determining chemical structure is X-ray diffraction.
en.wikipedia.org /wiki/Chemical_structure   (97 words)

  
 Education Resources » Chemical reaction
Chemical reactions are characterized by a chemical change and it yields one or more products which are different from the reactants.
Classically, chemical reactions encompass changes that strictly involve the motion of electrons in the forming and breaking of chemical bonds, although the general concept of a chemical reaction, in particular the notion of a chemical equation, is applicable to transformations of elementary particles, as well as nuclear reactions.
Chemical reactions may be classified in different ways depending on the particular aspect considered for elaborating the division, or on the branch of Chemistry which the classification originates from.
www.thecatalyst.org /resource/2006/04/21/Chemical-reaction   (1554 words)

  
 Latest Full-Text Prion Articles
Samples lyophilized from 50% acetonitrile/50% water show chemical shifts characteristic of a beta-sheet conformation in the region corresponding to residues 112-121, whereas samples lyophilized from hexafluoroisopropanol display shifts indicative of alpha-helical secondary structure in the region corresponding to residues 113-117.
These chemical shifts predominately reflect the local conformations of the peptides and are largely independent of the identity of neighboring residues.
Chemical shifts of amino acid carbons in the solid state in a beta-sheet conformation differ by as much as 8 ppm from those in an alpha-helix (Saito, 1986).
www.mad-cow.org /~tom/upcoming_3D.html   (1617 words)

  
 JIS: Tschinkel 2.12.2002
C chemical shift of solid materials is known to be sensitive to the crystal form (Kameda et al.
At the melting temperature, the peak intensity at 30.3 ppm increased, whereas the broad peak at 32.9 ppm was missing as shown in Fig.
Although the relationship between the crystal forms and its corresponding NMR chemical shifts for the beeswax is unclear, it can be said that several kinds of crystal forms exist in the crystal region of the beeswax.
www.insectscience.org /4.29   (3021 words)

  
 Recent Studies in Nicotine Chemistry - III
Findings indicate "that a knowledge of conformation is essential for an understanding of the chemical personality of nicotine and its analogues." Abstract quoted in full: "The synthesis in our laboratories of a wide variety of nicotine analogues has served as the basis for a range of chemical and pharmacological investigations.
We have examined the effect of substituents on nicotine's structure, conformation, and chemical r~activity: A chemical model for nicotinic activity has been developed by a thorough evaluation of the methylation of these analogues, thereby simultaneousl~ quantifying the relative and absolute nitrogen nucleophilicities of these nicotinoids.
THIE CONFORMATION OF NICOTINE Specification of..: nicotine's conformation requires definitien of three stereochemical fe.atures: (a) the orientation of the pyrrolidine N'-methyl group relative t3 the pyridine ring (cis as in ~7, trans as in ~8); the conforma- tion of ithe five membered pyrrolidine ring; and the orientation of the pyridine ring relative to the.
tobaccodocuments.org /ahf/2021579716-9771.html   (1672 words)

  
 NMR Structure of the {alpha}-Hemoglobin Stabilizing Protein: INSIGHTS INTO CONFORMATIONAL HETEROGENEITY AND BINDING -- ...   (Site not responding. Last check: 2007-09-17)
C chemical shifts of proline residues in proteins (18).
Summary of conformational constraints and statistics for the 20 accepted structures of AHSP (cis and trans conformers) and the P30A mutant Calculated structures were accepted when no distance violations were greater than 0.3 Å, no angle violations were greater than 5.0°, and no RDC violations were greater than 2.5 Hz.
The resonances corresponding to the cis and the trans conformations of the wild-type AHSP are labeled as c and t, respectively.
www.jbc.org /cgi/content/full/279/33/34963   (3828 words)

  
 Hormones and Health
Activation or deactivation of chemical messages occurs as the signal is passed from one molecular receptor to the next.
Additional experiments using knockout mice for the ER growth factor indicate there is a complex molecular pathway of interactions in which estrogen acts on mammary stromal cells via the ER to elicit a crucial estrogen growth factor receptor that in turn elicits the release of another factor causing growth of the mammary epithelial cells.
Diethylstilbestrol (DES), a synthetic chemical that acts like natural estrogen and that was widely prescribed to pregnant women in the 1950s and 1960s to prevent miscarriage, among other uses, provides an early example of the effects of hormone-disrupting chemicals on humans.
www.p2pays.org /ref/06/05386.htm   (4320 words)

  
 Probing Conformational Disorder in Neurotensin by Two-Dimensional Solid-State NMR and Comparison to Molecular Dynamics ...
The conformation of neurotensin bound to its G protein-coupled receptor.
Secondary chemical shifts in immobilized peptides and proteins: a qualitative basis for structure refinement under magic angle spinning.
Quantification of conformational disorder in glassy polycarbonate by two-dimensional nuclear magnetic resonance spectroscopy.
www.biophysj.org /cgi/content/full/89/3/2113   (3701 words)

  
 [No title]   (Site not responding. Last check: 2007-09-17)
Similarly, the functional properties of an enzyme might be manipulated in real-time as part of a method for detection of chemical and biological agents or as part of a new countermeasure for chemical and biological defense.
Indirect methods of measuring protein conformation, such as the measurement of ionic currents with a patch clamp, are not viewed as useful for this program unless they are coupled with a single protein measurement.
Computational approaches for modeling the conformational change in proteins that are relevant to chemical and biological countermeasures are required to correlate measurements with a physical understanding of the processes.
www.darpa.mil /baa/baa06-19mod2.html   (1791 words)

  
 Intramolecular secondary structure rearrangement by the kissing interaction of the Neurospora VS ribozyme -- Andersen ...
Nucleotides in the lower part of stem-loop I involved in the conformational change are indicated by fl boxes (22).
Chemical Modification Reveals the Kissing Interaction Is Required for the Secondary-Structure Rearrangement of Stem-Loop I. To extend our previous investigation of the role of the loop I-V kissing interaction in the self-cleavage of VS RNA (6),
was consistent with the unshifted conformation of stem-loop I: C634 was not reactive with DMS (lane 5).
www.pnas.org /cgi/content/full/98/14/7730   (5044 words)

  
 Conformational isomerism - Wikipedia, the free encyclopedia
The E2 elimination mechanism relies on the base- or acid-attacked substituent being in an antiperiplanar configuration along a bond with respect to the leaving group.
A combination of axial and equatorial substituents cannot react through an E2 mechanism, though ring flips (with associated reconformation) may allow reactions to occur if they are not precluded by an energy barrier or steric lock through isopropyl or larger substituents.
Conformational isomerism only occurs around single bonds because double or triple bonds have one or two pi bonds that prevent rotation about the longitudinal axis.
en.wikipedia.org /wiki/Chemical_conformation   (502 words)

  
 Monday and Tuesday Posters (3)
The peaks in both spectra have similar chemical shifts, particularly of the backbone carbons, which is indicative of similarities in the overall structures of normal and defective elastin.
From the 13C and 1H isotropic chemical shift values, it is predicted that the main chain conformations of tetraalanine and PLA-200 are mainly beta-sheet while the conformation of PLA-333 is mainly an alpha-helix.
C chemical shift tensor of the carbonyl carbon in the case where the a-helix is freely rotating in the magnetically oriented membranes about the helical axis.
www.enc-conference.org /1999abstracts/m_t3.htm   (6686 words)

  
 B and C
C-C(Y)=X (with identical or different groups R) the conformation in which the torsion angle is such that X is antiperiplanar to one of the groups R, and, in a Newman projection, the double bond C=X bisects one of the R-C-R angles.
In a five-membered ring a conformation in which two adjacent atoms are maximally displaced, in opposite directions, relative to the plane containing the other three carbon atoms has been called a half-chair but is better called a twist conformation (see also envelope conformation).
A set of chemically identical atomic or molecular structural units in a solid array or of chemically identical molecular entities that can explore the same set of molecular energy levels on the time scale of the experiment.
www.chem.qmul.ac.uk /iupac/stereo/BC.html   (1536 words)

  
 Chemical Kinetics
Chemical kinetics is the study of chemical (or biological) systems whose composition changes with time.
In biological systems, for example, the cellular machinery involves a very large number of chemical reactions catalyzed by proteins, association (and dissociation) of proteins with other proteins and with DNA molecules, and conformational changes in the stucture of the biological molecules.
The spontaneous fluctuation of the structure of a protein molecule from one conformation to another is an example of a unimolecular reaction.
www.uic.edu /classes/phys/phys461/phys450/ANJUM06   (1458 words)

  
 In This Issue : Nature Chemical Biology
Siderophores, chemicals that are secreted by bacteria to capture the necessary iron to grow during infection, offer an untapped target.
This small molecule represents a potential new therapeutic lead against tuberculosis and plague, and a chemical probe for further investigating the role of siderophores during infection.
In this approach, a small label, with chemical reactivity distinct from that of biologically occurring molecules, is attached to the desired biomolecule by cellular machinery and detected by selective reaction with a probe.
www.nature.com /nchembio/journal/v1/n1/full/nchembio0605-1.html   (699 words)

  
 CBP Course Descriptions   (Site not responding. Last check: 2007-09-17)
The structure, chemical properties, and methods of preparation of the more important classes of carbon compounds are studied, with an emphasis on the relationship of structure, stereochemistry, and conformation to chemical reactivity.
The periodic table as a tool for predicting the physical and chemical properties of chemical systems is developed and examined in conjunction with various theories of bonding, including valence bond, molecular orbital, valance shell, electron repulsion, and ligand field theory.
The effects of the chemical bond on the structure and properties of molecules and solids are investigated.
arrhenius.rider.edu /chemistry/coursedesc.html   (2129 words)

  
 Silverman Lab, Dept. of Chemistry, University of Illinois at Urbana-Champaign
We capitalize on these favorable chemical and physical properties by using DNA as a structural constraint to control the conformations of other molecules.
For the macromolecule whose conformation is controlled, we initially chose the P4-P6 domain of the Tetrahymena group I intron RNA, which is a structurally well-characterized large RNA (160 nucleotides, molecular weight ~51000; see Fundamental studies of RNA folding and catalysis).
That is, the DNA constraint is a "mismatch" with the RNA conformation.
www.scs.uiuc.edu /~scott/DNAconstraint.html   (1644 words)

  
 Characterization of a novel type VII {beta}-turn conformation for a bio-active tetrapeptide rigin: A synergy between ...   (Site not responding. Last check: 2007-09-17)
Characterization of a novel type VII {beta}-turn conformation for a bio-active tetrapeptide rigin: A synergy between theoretical and experimental results -- Ashish et al.
conformation of the methylene units of the Arg side-chain is
The characterization of the molecular conformation of rigin
content.febsjournal.org /cgi/content/full/267/5/1455   (4083 words)

  
 Relationship among Location of T-Antigen-Induced DNA Distortion, Auxiliary Sequences, and DNA Replication Efficiency -- ...
Conformational changes in the regulatory regions of pC133 (A to C) and pC163 (D).
P-labeled fragment was probed with adozelesin, the chemical probe for bent DNA (A); bizelesin, the chemical probe for straight DNA (B); or hedamycin, the chemical probe for unwound DNA (C and D).
Conformational changes in simian virus 40 rearranged regulatory regions: effects of the 21-base-pair promoters and their location.
jvi.asm.org /cgi/content/full/77/19/10651   (4326 words)

  
 [No title]
The chemical reactions that occur inside cells are directly controlled by a large set of protein molecules called enzymes, whose functions depend on their specific shapes.
The sequence of amino acids and the shape of the chain are a consequence of attractions between the chain’s parts.
The breakdown of nutrient molecules enables all cells to store energy in specific chemicals that are used to carry out the life functions of the cell.
www.fcps.k12.va.us /PimmitAltHS/SOL_EOC/Science/ScienceCF-BIO.htm   (3023 words)

  
 Butler University - College of Liberal Arts and Sciences
Many of the laws, theories and principles that we will be discussing are considered to be among the great intellectual achievements of the 19 th and 20 th centuries.
Other fundamental chemical concepts, such as chemical equilibria, thermodynamics, kinetics (uncatalyzed versus catalyzed), stereochemistry, conformation, and chemical mechanism will also be examined within a biological context.
On the surface, this course is content-driven, a necessity dictated at least partially by external expectations for a "biochemical" education by educational bodies such as the American Chemical Society.
www.butler.edu /las/ChemistrySy.aspx   (2375 words)

  
 Sites on Calmodulin That Interact with the C-terminal Tail of Cav1.2 Channel -- Xiong et al. 280 (8): 7070 -- Journal ...   (Site not responding. Last check: 2007-09-17)
Chemical shifts for the 11 amino acids are identical for Ca -CaM
The mean plus one S.D. of chemical shift differences for all residues of 0.46 ppm (dashed line) is used as reference for very significant changes.
that the IQ-peptide alters the conformation of the N-lobe to
www.jbc.org /cgi/content/full/280/8/7070   (6338 words)

  
 The role of irregular unit, GAAS, on the secondary structure of Bombyx mori silk fibroin studied with 13C CP/MAS NMR ...
chemical shifts were 48.8 and 42.5 ppm, respectively.
chemical shift contour line is quite different in the case of
Fraser, R.D.B. and MacRae, T.P. Conformations of fibrous proteins and related synthetic polypeptides.
www.proteinscience.org /cgi/content/full/11/8/1873   (2186 words)

  
 Penn Department of Chemistry - Faculty   (Site not responding. Last check: 2007-09-17)
A large series of synthetic metals can be formed either by chemical or electrochemical polymerization of aniline or its derivatives.
Stretch-alignment of films and fibers of the polymer results in an approximately 100-fold increase in conductivity in the direction of polymer chain alignment.
Synthetic, structural, physical, and electrochemical studies of these polymers and their ring- and N-substituted derivatives are presently being performed in order to better understand factors, including molecular conformation, which control their conductivity and chemical and physical properties.
www.sas.upenn.edu /chem/faculty/macdiarmid/macdiarmid.html   (383 words)

  
 Chemical Chaperones Enhance Superantigen and Conventional Antigen Presentation by HLA-DM-Deficient as well as ...
B, Thymidine incorporation by CTLL in response to undiluted culture supernatant is plotted as a function of chemical chaperone concentration.
Effect of chemical chaperone pre-treatment on the ability of low density but not high density membrane fractions to present HEL46-61 to T cells.
Influences of molecular and chemical chaperones on protein folding.
www.jimmunol.org /cgi/content/full/161/7/3262   (5490 words)

  
 The Mechanochemistry of Molecular Motors -- Keller and Bustamante 78 (2): 541 -- Biophysical Journal
chemical axis is accompanied by a chemical change (with its associated
Each macroscopic species is identified with a minimum of the potential, and transitions between species are associated with low energy pathways between minima.
Consider a single first-order chemical process, say, between species C and species A through the trough in the middle of Fig.
www.biophysj.org /cgi/content/full/78/2/541   (5646 words)

  
 Prediction of Organophosphorus Acetylcholinesterase Inhibition Using Three-Dimensional Quantitative Structure-Activity ...
) and the number of conformations generated for each compound are also indicated.
Computer graphic illustration of the pharmacophore P1S represented by solid objects in cyan, green, and brown, superimposed with the shape query (gray) corresponding to the conformation of 1 in its overlap with P1.
Wallace, K. B., and Kemp, J. Species specificity in the chemical mechanisms of organophosphorus anticholinesterase activity.
toxsci.oxfordjournals.org /cgi/content/full/63/2/223   (4662 words)

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