You are using an unsupported browser. Please upgrade your browser to a newer version to get the best experience on Human Metabolome Database.
Record Information
Version4.0
StatusDetected and Quantified
Creation Date2005-11-16 15:48:42 UTC
Update Date2017-10-23 17:11:42 UTC
HMDB IDHMDB0000133
Secondary Accession Numbers
  • HMDB00133
Metabolite Identification
Common NameGuanosine
DescriptionGuanosine is a nucleoside comprising guanine attached to a ribose (ribofuranose) ring via a beta-N9-glycosidic bond. Guanosine can be phosphorylated to become GMP (guanosine monophosphate), cGMP (cyclic guanosine monophosphate), GDP (guanosine diphosphate) and GTP (guanosine triphosphate). (Wikipedia). The nucleoside guanosine exert important neuroprotective and neuromodulator roles in the central nervous system, which may be related to inhibition of the glutamatergic neurotransmission activity. Guanosine is the specific extracellular guanine-based purines effector and indicate that its conversion occurs not only in the central nervous system but also peripherally. (PMID: 16325434 ).
Structure
Thumb
Synonyms
ValueSource
2(3H)-imino-9-beta-D-Ribofuranosyl-9H-purin-6(1H)-oneChEBI
2-amino-1,9-dihydro-9-beta-D-Ribofuranosyl-6H-purin-6-oneChEBI
2-amino-9-beta-D-Ribofuranosyl-1,9-dihydro-6H-purin-6-oneChEBI
9-beta-D-Ribofuranosyl-guanineChEBI
GChEBI
Guanine ribosideChEBI
Guanine-9-beta-D-ribofuranosideChEBI
GuanosinChEBI
GuoChEBI
2(3H)-imino-9-b-D-Ribofuranosyl-9H-purin-6(1H)-oneGenerator
2(3H)-imino-9-β-D-ribofuranosyl-9H-purin-6(1H)-oneGenerator
2-amino-1,9-dihydro-9-b-D-Ribofuranosyl-6H-purin-6-oneGenerator
2-amino-1,9-dihydro-9-β-D-ribofuranosyl-6H-purin-6-oneGenerator
2-amino-9-b-D-Ribofuranosyl-1,9-dihydro-6H-purin-6-oneGenerator
2-amino-9-β-D-ribofuranosyl-1,9-dihydro-6H-purin-6-oneGenerator
9-b-D-Ribofuranosyl-guanineGenerator
9-β-D-ribofuranosyl-guanineGenerator
Guanine-9-b-D-ribofuranosideGenerator
Guanine-9-β-D-ribofuranosideGenerator
2-amino-1,9-dihydro-9-beta-delta-Ribofuranosyl-6H-purin-6-oneHMDB
2-amino-InosineHMDB
9-beta-delta-Ribofuranosyl-guanineHMDB
b-D-Ribofuranoside guanine-9HMDB
beta-delta-Ribofuranoside guanine-9HMDB
RibonucleosideHMDB
VernineHMDB
Chemical FormulaC10H13N5O5
Average Molecular Weight283.2407
Monoisotopic Molecular Weight283.091668551
IUPAC NameNot Available
Traditional NameNot Available
CAS Registry Number118-00-3
SMILESNot Available
InChI Identifier
InChI=1S/C10H13N5O5/c11-10-13-7-4(8(19)14-10)12-2-15(7)9-6(18)5(17)3(1-16)20-9/h2-3,5-6,9,16-18H,1H2,(H3,11,13,14,19)/t3-,5-,6-,9-/m1/s1
InChI KeyNYHBQMYGNKIUIF-UUOKFMHZSA-N
Chemical Taxonomy
DescriptionThis compound belongs to the class of chemical entities known as purine nucleosides. These are compounds comprising a purine base attached to a ribosyl or deoxyribosyl moiety.
KingdomChemical entities
Super ClassOrganic compounds
ClassNucleosides, nucleotides, and analogues
Sub ClassPurine nucleosides
Direct ParentPurine nucleosides
Alternative Parents
Substituents
  • Purine nucleoside
  • Glycosyl compound
  • N-glycosyl compound
  • Pentose monosaccharide
  • Imidazopyrimidine
  • Purine
  • Hydroxypyrimidine
  • Monosaccharide
  • N-substituted imidazole
  • Pyrimidine
  • Azole
  • Imidazole
  • Heteroaromatic compound
  • Oxolane
  • Secondary alcohol
  • Oxacycle
  • Azacycle
  • Organoheterocyclic compound
  • Organic nitrogen compound
  • Alcohol
  • Hydrocarbon derivative
  • Organopnictogen compound
  • Organic oxygen compound
  • Organonitrogen compound
  • Organooxygen compound
  • Primary alcohol
  • Aromatic heteropolycyclic compound
Molecular FrameworkAromatic heteropolycyclic compounds
External Descriptors
Ontology
Physiological effect

Health effect:

  Health condition:

Disposition

Biological Location:

  Subcellular:

  Biofluid and excreta:

  Organ and components:

Source:

Process

Naturally occurring process:

  Biological process:

    Biochemical pathway:

Role

Industrial application:

  Pharmaceutical industry:

Indirect biological role:

Physical Properties
StateSolid
Experimental Properties
PropertyValueReference
Melting Point239 °CNot Available
Boiling PointNot AvailableNot Available
Water Solubility0.7 mg/mL at 18 °CNot Available
LogP-1.90SANGSTER (1993)
Predicted PropertiesNot Available
Spectra
Spectra
Spectrum TypeDescriptionSplash Key
GC-MSGC-MS Spectrum - GC-EI-TOF (Pegasus III TOF-MS system, Leco; GC 6890, Agilent Technologies) (5 TMS)splash10-0f7k-1952000000-c57c052c65f3fa9504afView in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Pegasus III TOF-MS system, Leco; GC 6890, Agilent Technologies) (Non-derivatized)splash10-0feb-0963000000-c91b93f300b50fbc99c1View in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Pegasus III TOF-MS system, Leco; GC 6890, Agilent Technologies) (4 TMS)splash10-00di-9440000000-361092fc2dc5206fe655View in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Pegasus III TOF-MS system, Leco; GC 6890, Agilent Technologies) (5 TMS)splash10-00di-9421000000-b2b15c03b8206196f59fView in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Non-derivatized)splash10-0f7k-1952000000-c57c052c65f3fa9504afView in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Non-derivatized)splash10-0feb-0963000000-c91b93f300b50fbc99c1View in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Non-derivatized)splash10-00di-9440000000-361092fc2dc5206fe655View in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Non-derivatized)splash10-00di-9421000000-b2b15c03b8206196f59fView in MoNA
Predicted GC-MSPredicted GC-MS Spectrum - GC-MS (Non-derivatized) - 70eV, Positivesplash10-0zml-9670000000-793c36e66ed6430b932bView in MoNA
Predicted GC-MSPredicted GC-MS Spectrum - GC-MS (3 TMS) - 70eV, Positivesplash10-0159-4945800000-86e8114119c47d85cc53View in MoNA
LC-MS/MSLC-MS/MS Spectrum - Quattro_QQQ 10V, Positive (Annotated)splash10-0udi-0900000000-ef0cae7d67f9e803f2b2View in MoNA
LC-MS/MSLC-MS/MS Spectrum - Quattro_QQQ 25V, Positive (Annotated)splash10-0udi-0900000000-68fb606342b8bb123bb7View in MoNA
LC-MS/MSLC-MS/MS Spectrum - Quattro_QQQ 40V, Positive (Annotated)splash10-0f89-0900000000-48d32b9d62eda760619eView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-0f7k-0920000000-f3db23cc762b5fb860e4View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-001i-0900000000-5da62630f03e15d8707cView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-001i-0900000000-1fa2eb473b57a37ecd45View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-0udi-0900000000-d71a3d2995d32c692eb7View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-001i-0390000000-ff54fe98a9c0e1bc104cView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-001i-0900000000-c023445b0f47e6e7267bView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-0udi-0900000000-a094aa75c261cdce24deView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Positivesplash10-0udi-0900000000-e114cc69f7ab438abb39View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-001j-0795222100-55ad26c7c4d9f64dd759View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-004i-0900000000-9450dc04b32ca468e146View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-0002-0900000000-0147dd895ffbecfa9668View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-03di-0190000000-5d00bb466dd23f062b86View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-0f89-0690030010-86fae3a6cae3e2b3de2cView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-001i-0900000000-97217b0084eeac14e7e1View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-0udi-0900000000-d0c65e36192b7ebdaae8View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-ITFT (LTQ Orbitrap XL, Thermo Scientfic) , Negativesplash10-001i-0090000000-bb8ef433eba795395fe3View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-QQ (API3000, Applied Biosystems) 10V, Negativesplash10-001i-0090000000-4ceff605ca97b7c0774aView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-QQ (API3000, Applied Biosystems) 20V, Negativesplash10-0ue9-0960000000-1c286e55d437f33a29b3View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-QQ (API3000, Applied Biosystems) 30V, Negativesplash10-0udi-0900000000-7149427a8c09f429fdbeView in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-QQ (API3000, Applied Biosystems) 40V, Negativesplash10-0zgi-0900000000-5de849ca7144ca8afe05View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-QQ (API3000, Applied Biosystems) 50V, Negativesplash10-053r-0900000000-f97dbc10f152af4df778View in MoNA
LC-MS/MSLC-MS/MS Spectrum - LC-ESI-QQ (API3000, Applied Biosystems) 10V, Positivesplash10-0ue9-0970000000-045435f1be487a94195cView in MoNA
1D NMR1H NMR SpectrumNot AvailableView in JSpectraViewer
1D NMR13C NMR SpectrumNot AvailableView in JSpectraViewer
2D NMR[1H,1H] 2D NMR SpectrumNot AvailableView in JSpectraViewer
2D NMR[1H,13C] 2D NMR SpectrumNot AvailableView in JSpectraViewer
Biological Properties
Cellular Locations
  • Extracellular
  • Mitochondria
  • Lysosome
Biofluid Locations
  • Blood
  • Cellular Cytoplasm
  • Feces
  • Saliva
  • Urine
Tissue Location
  • Prostate
Pathways
NameSMPDB/PathwhizKEGG
AICA-RibosiduriaPw000082Pw000082 greyscalePw000082 simpleNot Available
Adenine phosphoribosyltransferase deficiency (APRT)Pw000511Pw000511 greyscalePw000511 simpleNot Available
Adenosine Deaminase DeficiencyPw000075Pw000075 greyscalePw000075 simpleNot Available
Adenylosuccinate Lyase DeficiencyPw000076Pw000076 greyscalePw000076 simpleNot Available
Azathioprine PathwayPw000266Pw000266 greyscalePw000266 simpleNot Available
Normal Concentrations
BiofluidStatusValueAgeSexConditionReferenceDetails
BloodDetected and Quantified0.8 +/- 0.5 uMAdult (>18 years old)BothNormal details
Cellular CytoplasmDetected and Quantified4.5 +/- 2.9 uMAdult (>18 years old)BothNormal details
FecesDetected but not Quantified Not SpecifiedBoth
Normal
details
FecesDetected but not Quantified Children (6 - 18 years old)Not SpecifiedNormal details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected but not Quantified Adult (>18 years old)Male
Normal
details
SalivaDetected and Quantified0.101 +/- 0.0647 uMAdult (>18 years old)BothNormal
    • Sugimoto et al. (...
details
SalivaDetected and Quantified0.227 +/- 0.617 uMAdult (>18 years old)Female
Normal
    • Sugimoto et al. (...
details
SalivaDetected and Quantified0.262 +/- 0.285 uMAdult (>18 years old)Female
Normal
    • Sugimoto et al. (...
details
UrineDetected and Quantified0.13 (0.022-0.23) umol/mmol creatinineAdult (>18 years old)BothNormal details
UrineDetected and Quantified0.06 +/- 0.02 umol/mmol creatinineAdult (>18 years old)FemaleNormal details
UrineDetected and Quantified0.05 +/- 0.02 umol/mmol creatinineAdult (>18 years old)BothNormal details
UrineDetected and Quantified0.06 +/- 0.02 umol/mmol creatinineAdult (>18 years old)BothNormal details
UrineDetected and Quantified0-11 umol/mmol creatinineChildren (1 - 18 years old)Both
Normal
    • BC Children's Hos...
details
UrineDetected and Quantified7.8 +/- 8.736 umol/mmol creatinineChildren (1 - 13 years old)Not Specified
Normal
    • Mordechai, Hien, ...
details
Abnormal Concentrations
BiofluidStatusValueAgeSexConditionReferenceDetails
FecesDetected but not Quantified Adult (>18 years old)BothColorectal Cancer details
FecesDetected but not Quantified Children (6 - 18 years old)BothCrohns disease details
FecesDetected but not Quantified Children (6 - 18 years old)BothUlcerative colitis details
FecesDetected but not Quantified Children (6 - 18 years old)Not SpecifiedCrohns disease details
FecesDetected but not Quantified Children (6 - 18 years old)Not SpecifiedUlcerative colitis details
FecesDetected but not Quantified Children (6 - 18 years old)Not SpecifiedUnclassified IBD details
FecesDetected but not Quantified Adult (>18 years old)BothColorectal Cancer details
SalivaDetected and Quantified0.0609 +/- 0.0661 uMAdult (>18 years old)BothTooth alignment disorders
    • Sugimoto et al. (...
details
UrineDetected and Quantified35.0 - 2588.0 umol/mmol creatinineAdult (>18 years old)BothPurine nucleoside phosphorylase (PNP) deficiency details
UrineDetected and Quantified35-588 umol/mmol creatinineAdult (>18 years old)BothPurine nucleoside phosphorylase (PNP) deficiency details
UrineDetected and Quantified13.601 +/- 7.764 umol/mmol creatinineChildren (1 - 13 years old)Not Specified
Eosinophilic esophagitis
    • Mordechai, Hien, ...
details
Associated Disorders and Diseases
Disease References
Purine nucleoside phosphorylase deficiency
  1. Wevers RA, Engelke UF, Moolenaar SH, Brautigam C, de Jong JG, Duran R, de Abreu RA, van Gennip AH: 1H-NMR spectroscopy of body fluids: inborn errors of purine and pyrimidine metabolism. Clin Chem. 1999 Apr;45(4):539-48. [PubMed:10102915 ]
Associated OMIM IDs
  • 164050 (Purine nucleoside phosphorylase deficiency )
DrugBank IDDB02857
DrugBank Metabolite IDNot Available
Phenol Explorer Compound IDNot Available
Phenol Explorer Metabolite IDNot Available
FoodDB IDFDB003632
KNApSAcK IDNot Available
Chemspider ID6544
KEGG Compound IDC00387
BioCyc IDGUANOSINE
BiGG ID51567
Wikipedia LinkGuanosine
METLIN ID87
PubChem Compound6802
PDB IDGMP
ChEBI ID16750
References
Synthesis ReferenceTang, Shengrong; Huang, Weihong; Hou, Zuorong. Process of guanosine production by fermentation. Gongye Weishengwu (1998), 28(4), 11-16.
Material Safety Data Sheet (MSDS)Download (PDF)
General References
  1. Sreekumar A, Poisson LM, Rajendiran TM, Khan AP, Cao Q, Yu J, Laxman B, Mehra R, Lonigro RJ, Li Y, Nyati MK, Ahsan A, Kalyana-Sundaram S, Han B, Cao X, Byun J, Omenn GS, Ghosh D, Pennathur S, Alexander DC, Berger A, Shuster JR, Wei JT, Varambally S, Beecher C, Chinnaiyan AM: Metabolomic profiles delineate potential role for sarcosine in prostate cancer progression. Nature. 2009 Feb 12;457(7231):910-4. doi: 10.1038/nature07762. [PubMed:19212411 ]
  2. Lee SH, Jung BH, Kim SY, Chung BC: A rapid and sensitive method for quantitation of nucleosides in human urine using liquid chromatography/mass spectrometry with direct urine injection. Rapid Commun Mass Spectrom. 2004;18(9):973-7. [PubMed:15116424 ]
  3. Traut TW: Physiological concentrations of purines and pyrimidines. Mol Cell Biochem. 1994 Nov 9;140(1):1-22. [PubMed:7877593 ]
  4. Wevers RA, Engelke UF, Moolenaar SH, Brautigam C, de Jong JG, Duran R, de Abreu RA, van Gennip AH: 1H-NMR spectroscopy of body fluids: inborn errors of purine and pyrimidine metabolism. Clin Chem. 1999 Apr;45(4):539-48. [PubMed:10102915 ]
  5. Hartwick RA, Krstulovic AM, Brown PR: Identification and quantitation of nucleosides, bases and other UV-absorbing compounds in serum, using reversed-phase high-performance liquid chromatography. II. Evaluation of human sera. J Chromatogr. 1979 Dec 30;186:659-76. [PubMed:546939 ]
  6. Saute JA, da Silveira LE, Soares FA, Martini LH, Souza DO, Ganzella M: Amnesic effect of GMP depends on its conversion to guanosine. Neurobiol Learn Mem. 2006 May;85(3):206-12. Epub 2005 Dec 1. [PubMed:16325434 ]

Enzymes

General function:
Involved in hydrolase activity
Specific function:
Hydrolyzes extracellular nucleotides into membrane permeable nucleosides.
Gene Name:
NT5E
Uniprot ID:
P21589
Molecular weight:
57948.125
Reactions
Guanosine monophosphate + Water → Guanosine + Phosphoric aciddetails
General function:
Involved in nucleotide binding
Specific function:
Dephosphorylates the 5' and 2'(3')-phosphates of deoxyribonucleotides. Helps to regulate adenosine levels (By similarity).
Gene Name:
NT5C1B
Uniprot ID:
Q96P26
Molecular weight:
68803.055
Reactions
Guanosine monophosphate + Water → Guanosine + Phosphoric aciddetails
General function:
Involved in nucleotide binding
Specific function:
Dephosphorylates the 5' and 2'(3')-phosphates of deoxyribonucleotides and has a broad substrate specificity. Helps to regulate adenosine levels in heart during ischemia and hypoxia.
Gene Name:
NT5C1A
Uniprot ID:
Q9BXI3
Molecular weight:
41020.145
Reactions
Guanosine monophosphate + Water → Guanosine + Phosphoric aciddetails
General function:
Involved in metal ion binding
Specific function:
Dephosphorylates the 5' and 2'(3')-phosphates of deoxyribonucleotides, with a preference for dUMP and dTMP, intermediate activity towards dGMP, and low activity towards dCMP and dAMP.
Gene Name:
NT5C
Uniprot ID:
Q8TCD5
Molecular weight:
Not Available
Reactions
Guanosine monophosphate + Water → Guanosine + Phosphoric aciddetails
General function:
Involved in phosphatase activity
Specific function:
Dephosphorylates specifically the 5' and 2'(3')-phosphates of uracil and thymine deoxyribonucleotides, and so protects mitochondrial DNA replication from excess dTTP. Has only marginal activity towards dIMP and dGMP.
Gene Name:
NT5M
Uniprot ID:
Q9NPB1
Molecular weight:
Not Available
Reactions
Guanosine monophosphate + Water → Guanosine + Phosphoric aciddetails
General function:
Involved in magnesium ion binding
Specific function:
Can act both as nucleotidase and as phosphotransferase.
Gene Name:
NT5C3
Uniprot ID:
Q9H0P0
Molecular weight:
33914.91
Reactions
Guanosine monophosphate + Water → Guanosine + Phosphoric aciddetails
General function:
Involved in 5'-nucleotidase activity
Specific function:
May have a critical role in the maintenance of a constant composition of intracellular purine/pyrimidine nucleotides in cooperation with other nucleotidases. Preferentially hydrolyzes inosine 5'-monophosphate (IMP) and other purine nucleotides.
Gene Name:
NT5C2
Uniprot ID:
P49902
Molecular weight:
64969.2
Reactions
Guanosine monophosphate + Water → Guanosine + Phosphoric aciddetails
General function:
Involved in purine-nucleoside phosphorylase activity
Specific function:
The purine nucleoside phosphorylases catalyze the phosphorolytic breakdown of the N-glycosidic bond in the beta-(deoxy)ribonucleoside molecules, with the formation of the corresponding free purine bases and pentose-1-phosphate.
Gene Name:
PNP
Uniprot ID:
P00491
Molecular weight:
32117.69
Reactions
Guanosine + Phosphoric acid → Guanine + Ribose 1-phosphatedetails
References
  1. Overington JP, Al-Lazikani B, Hopkins AL: How many drug targets are there? Nat Rev Drug Discov. 2006 Dec;5(12):993-6. [PubMed:17139284 ]
  2. Imming P, Sinning C, Meyer A: Drugs, their targets and the nature and number of drug targets. Nat Rev Drug Discov. 2006 Oct;5(10):821-34. [PubMed:17016423 ]