ARGENTINA FCENA-UNNE Theoretical analysis of measurable NMR spectroscopic parameters in medium-size acyclic hydrocarbons and H-bonded aminoacids * , Patricio F. Provasi * , Marina Sanchez * and Gustavo A. Aucar Stephan P. A. Sauer # * Physics Department - Northeastern University – Argentina # Chemistry Department - Copenhagen University – Denmark 1 IANANO 2005
ARGENTINA FCENA-UNNE � NMR Spectroscopy – Phenomenology � Experimental and Theoretical description � NR theory � Ramsey mechanisms � Requirements for reliable calculations � Polarization propagator approach � Long-range F-F and C-F couplings. Shieldings. Its application to QCs. � H-bonded aminoacids 2 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Periodic Table 3 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Phenomenology 4 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Spectral origin 5 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Spectral lines 6 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Experiments � Spectroscopic parameters: Indirect nuclear spin couplings: J [Hz] � ppm] �[ Nuclear magnetic shieldings: (Chemical shift: � ) � Gas – liquid – solid For solids the main spin-spin relaxation is dip-dip interactions. Decoherence times: For solids, few milliseconds For liquid, several seconds � Measurements. First order spectra. Error bars 7 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Theoretical studies � Electronic mechanisms � Non relativistic theory. Ramsey: FC, SD, PSO, SDO � Reliable calculations from ab initio methods: � Electronic correlation (MCSCF, SOPPA, EOM-CCSD) � Basis sets � Rovibrational effects � Relativity 8 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Fluorinated organic compounds � Growing interest of Fluorinated organic compounds: � Biological activity � Fluorine incorporated to: Alpha-helices, proteins and bioactive small molecules as NMR probes for aggregation, microenvironmental structure and binding site interactions. � Unusually large F-F couplings in unsaturated compounds � Previous studies on the application of NMR as quantum computers (QC) � Nuclear spins as quantum bits � The need for nonvanishing J-couplings in molecules of reasonable size. 9 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR quantum computers � The inherent power of a QC relies on the fact that the dimension of the Hilbert space grows exponentially with the number of particles allowing large-scale parallelization by exploiting the superposition principle of QM . Madi et al. JCP 109 , 10603 (1998). � Design of molecular NMR quantum computers: � Several criteria: 1. Prefered nuclei: 1 H, 13 C, 15 N, 19 F (I = ½ and high natural abundance) 2. Solubility. 3. Large J coupling between every pair of spins used as qubits. 4. Chemical shift not close between qubits. 5. Long enough spin-spin relaxation time. Liquid systems are the most suitable. 10 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR quantum computers – previous studies � R. C. Mawhinney and G. Schreckenbach; Magn. Reson. Chem. 42 , S88 (2004): “The two main challenges in NMR QC are the control of pulse imperfections and the design of molecular systems with the proper spectral properties “ 11 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR quantum computers – previous studies � R. C. Mawhinney and G. Schreckenbach; Magn. Reson. Chem. 42 , S88 (2004): “The two main challenges in NMR QC are the control of pulse imperfections and the design of molecular systems with the proper spectral properties “ � I. L. Chuang et al. PRL 85 , 5452 (2000): “Experimental realization of an order-finding algorithm with an NMR QC“. Finding the order of permutation. 12 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – New candidates 13 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – J(F-F) couplings 14 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – J(F-F) couplings 15 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – J(F-F) couplings 16 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – J(F-F) couplings and shieldings 17 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – J(C-F) couplings and shieldings 18 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – Shieldings 19 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded nucleic acid � Hidrogen bonds � Stabilization of protein and nucleic acid secondary structure � Modulate the speed and specificity of enzymatic reactions � NMR parameters � J coupling through H bonds is very important for structure determination. � Trans-hydrogen bond 3h J NC exist in proteins, like human ubiquitin (J ~ 0.25 to 0.92 Hz); Cornilescu et al JACS 121 , 2949 (1999), Cordier and Grzesiek JACS 121 , 1601 (1999). � Which are the mechanisms that controls the trans-hydrogen bonds in proteins? � Is it possible to predict their values? 20 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded nucleic acid Dingley and Grzesiek, JACS 120, 8293 (1998). J-correlation exp. for 69-nucleotide T1 domain of the potato spindle tuber viroid. Exp. d(N 3 – N 1 ) = 2.82 A J(N 3 – N 1 ) = 6.7 � 0.5 [Hz] Exp. d(N 3 – N 1 ) = 2.95 A J(N 3 – N 1 ) = 6.3 � 0.2 [Hz] 21 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded nucleic acid 22 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded nucleic acid 23 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded Fa-Fa 24 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded Fa-Fi d(N 1 – N 2 ): Ours 2.899 A Exp. 2.82 A – 2.95 A 25 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded Fa-Fa 26 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded Fa-Fa 27 GAA-IANANO 2005
ARGENTINA FCENA-UNNE NMR Spectroscopy – H-bonded Fa-Fa 28 GAA-IANANO 2005
ARGENTINA FCENA-UNNE Theoretical analysis of ... Summary Measurable NMR spectroscopic parameters in unsaturated fluorinated compounds � We have predicted measurable long-range F-F and C-F J-couplings (J > 1 Hz) in unsaturated compounds for distances longer than 1.2 nm. � The number of bond-separation between measurable coupled F-F and C-F nuclei is N > 9, which is longer than previous findings. � Fluorine substituted polyenes and polyynes are good candidates to be used as NMR QC. ... H-bonded aminoacids (Formamide-Formamide; Formamide-Formamidine) � Correlated ab initio calculations of NMR spectroscopic parameters of fragments of H-bonded aminoacids are available and give reliable results. � H-bonded H, O and C change their magnetic properties for Fa-Fa and Fa-Fi in such a way that it can be used not only for conformational studies but as a magnetic sensor. 29 GAA-IANANO 2005
ARGENTINA FCENA-UNNE Theoretical analysis of ... Sponsorship: National Research Council CONICET - Argentina Secretaria General de Ciencia y Técnica – UNNE – Argentina Danish Research Council - Denmark 30 GAA-IANANO 2005
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