核磁共振的内部构造.ppt

Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,*,This 15-minute presentation is identical to the one that runs continuously inside the,cut-up magnet display,in the Chemistry East hallway next to the E1-60 lecture theatre.,2009,Department of Chemistry,University of Alberta,Edmonton,Alberta,Canada,Copyright issues,You can download and use this PowerPoint presentation as you wish,provided,the file/presentation is not altered in any way,proper credit is given regarding the origin of the file,Designed for 24”1920 x 1200(16:10)LCD monitor,Created with PowerPoint 2003,Superconducting,200 MHz,NMR,Magnet,The hidden world of,N,uclear,M,agnet,R,esonance spectroscopy,This slide presentation is dedicated to the memory of,Glen Bigam,1939 2009,who worked in the NMR labs at the Department of Chemistry fornearly 50 years.,The picture shows Glen preparing this verymagnet for decommissioning in 2003.,This presentation is 15 minutes long and restarts automatically,What is NMR,what can it do?,Contents,Superconducting magnets:NMRs heart&soul,Sucrose as an example,Dissection of a magnet,Is NMR important?,3 Nobel prizes suggest it is:,1991,R.R.Ernst,Development of the methodology of high-resolution NMR spectroscopy,2002,K.Wthrich,Development of NMR spectros-copy for determining the 3-dimensional structure of biological macromolecules in solution,2003,P.C.Lauterbur&Sir P.Mansfield,Discoveries concerning magnetic resonance imaging(MRI),1991&2002:Switzerland,Chemistry,Chemistry,Medicine,2003:USA&UK,NMR comes in 4 different“flavors”,High-resolution,Solid-state,Magnetic Resonance,Imaging,(MRI),In vivo,NMR spectroscopy,samples in,solution,samples in,solid,form,pictures of tissue(common diagnostic tool in medicine),spectra of molecules in human or animal tissue,This magnet was used for,solution,NMR,What solution-state NMR can do,Study,interactions,of small molecules(drugs)with much larger molecules(proteins,viruses etc.),Confirm the structure,of,synthetic,compounds,Determine the,conformation,(=3-dimensional shape)of molecules in solution,Structure elucidation,of,unknown,compounds(e.g.natural products isolated from plants),What nuclei can be measured by NMR?,Most elements in the Periodic Table have at least one isotope that is NMR active,natural abundance,H1,100%,C12,99%,C13,1%,N15,0.4%,F19,100%,P31,100%,Most common:,H1,easy,100%abundance,isotopes,Not,useful:,C12,!,Fortunately there is,C13,Why MHz and not Tesla?,The strength of this magnet was 4.7 Tesla but it is referred to as a“,200,”,The basic frequency,w,0,of NMR-active nuclei is,proportional,to,Larmor,frequency:,200 MHz,for H1,magnetogyric constant,Conclusion:the basic H1 frequency gives it its name!,field:4.7 T,How strong is a field of 4.7 Tesla?,Earth:,0.00006,Tesla,2.5,k,Hz,This magnet:,4.7,Tesla,200,M,Hz,78,000,x,Strongest in Chemistry:,16.4,Tesla,700,M,Hz,273,000,x,Strongest commercially available:,22.3,Tesla,950,M,Hz,372,000,x,“standard”:,1,The heart&soul:superconducting wire,At 4 K(-269,C)the hair-like strands of metal alloy lose,all,resistance,Superconductivity!,Copper,matrix(,insulator,!?!,),tin-niobium-tantalum alloy(Sn-Nb-Ta),The,exact,composition of the alloy is a well kept secret,4K:liquid Helium,Superconductivity,You are not alone!Superconductivity is a,quantum mechanical,phenomenon that,cannot be understood in classical physics terms,.,=,zero,resistance at very low temperature,even near absolute zero copper retains some resistance,it is,not,the copper that made this a magnet,Hard to,understand,?,Keeping it,really,cold,room temperature,vacuum&reflective Mylar foil,50L liquid nitrogen,50L liquid Helium,vacuum&reflective Mylar foil,21,C,-,196,C,77 K,-,269,C,4 K,294 K,magnet solenoid,cryogens,Hollow on the inside!,vacuum&reflective Mylar foil,liquid nitrogen,liquid Helium,room temperature,vacuum&reflective Mylar foil,room temperature!,not to scale,magnet,solenoid,The proof,magnet bore:89 mm,more common:52 mm,The Journal is pictured through the magnet bore,Amps and wire,At installation(1979):charged with ca.35 amperes of electric current,Modern ultra high-field magnets use wire that,is several,hundred kilo-meters,long,can handle,hundreds of amps,not original design,cost up to,millions of$,Evaporation of cryogens,Despite the best insulation efforts(vacuum&Mylar foil),cryogens evaporate,slowly,To prevent buildup of ice where the cold gases exit,heat exchangers,are used,Magnet,operating cost:,electricity$0,cryogens:$5000/year,Quench,!,Quench:loss of superconductivity with very,rapid,(and,expensive,!)expulsion of helium gas,De-energizing of this magnet 2003-04-10,normal at first,suddenly not so normal!,$,$,$,$,$,$,NMR components,Magnets are the most eye-catching but not the only component of a complete system,Computer,Console:radio frequencies,Magnet,highly interactive!,The probe,Probe is inserted from the bottom,.samples go in from the top,Sample in the probe,electronic circuitry,probe sleeve removed,note receiver coils surrounding,red sample,Cost for probe:,$35,000,$300,000 cryo-cooled,What is a sample?,5 mm,glass tube,a few mg of compound,0.7 mL of a,deuterated,solvent(C,D,Cl3,D,2O and many more),The 200 used 10 and 20 mm tubes,displayed,below,is a 10 mm tube,Sucrose:a sweet example,Sucrose=table sugar!,ball&stick model,chemical structure,and the best 3-dimensional impression:a space-filling model,hydrogen,carbon,oxygen,NMR?,no,A bit of local sucrose&NMR history,Professor,Ray Lemieux,for whom this building is named,was the first person to chemically,synthesize,sucrose,in 1953,In 1982 he was the first to use NMR spectroscopy to deduce the,three-dimensional structure,of the,sucrose,molecule,H1 spectrum of sucrose at 600 MHz,Spectrometer records a,time,signal,seconds,0,1,2,F,ree,I,nduction,D,ecay(FID),5.0,4.0,FT,frequency or ppm,Scientists work with resulting,spectrum,Spectrum,F,ourier,T,ransformation by computer,Why strong magnets?,The,dispersion,of NMR signals is,proportional,to the field,Note the,separation,between the lines of sucrose at 90 MHz compared to 600 MHz,more details,easier&better analysis,Why strong magnets?,Higher,sensitivity,&better signal-to-noise ratio at higher field,Much smaller amounts of sample can be measured,noise,signal,600,vs.,300 MHz:600 is ca.,6,times better,600,300,Why strong magnets?,Spectral,simplification,Higher order,signal at 300 MHz,First order signal at 600 MHz,8 lines,instead of 4,4 lines,Easy inter-pretation of data,Dissection of a magnet,After over 20 years of service,the magnet(its surrounding tanks really)was cut in the Departments Machine Shop,March 2006,Randy Benson in full action,First cut of the seemingly endless layers of Mylar foil,Mylar reduces heat radiation-just like an outdoor emergency blanket,more Mylar cutting,after the Mylar,another tank,and back to more Mylar,3 layers of various metals,2 layers of Mylar,and still no magnet in sight!,Getting closer-at least it starts to look magnet-like,A magnet wrapped in hockey tape?,Careful peek behind the tape-this is not the magnet(yet)!,Next up:,cryoshim coils,purpose:improve the homogeneity of the magnet,Behind the cryo-shims another metal container,the magnet solenoid!,February 2007,finally,and,The last 3 steps side by side,The End,Thanks for watching!,Acknowledgments,magnet cutting,RANDY BENSON,display case design&build,PAUL CROTHERS,photography,DEPT.OF CHEMISTRY TOM BRISBANE JILL BAGWE,coordination&slide show,ALBIN OTTER,financial support,MARK MISKOLZIEALBIN OTTER,Interested in more NMR?,nmr.chem.ualberta.ca,might be of interest to you!,