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Record Information
Version5.0
StatusDetected and Quantified
Creation Date2007-05-30 12:04:10 UTC
Update Date2022-09-22 18:34:55 UTC
HMDB IDHMDB0006695
Secondary Accession Numbers
  • HMDB0029018
  • HMDB06695
  • HMDB29018
Metabolite Identification
Common NameProlylhydroxyproline
DescriptionProlylhydroxyproline is a dipeptide. Prolylhydroxyproline is a marker of bone collagen degradation, showing high sensitivity for the diagnosis of osteoporosis. Prolylhydroxyproline has been suggested as a possible alternative to hydroxyproline determination in bone resorption studies. Prolylhydroxyproline is one of the iminodipeptides present in the urine of patients with prolidase deficiency. Prolidase (X-Pro dipeptidase EC 3.4.13.9) splits iminodipeptides containing C-terminal proline or hydroxyproline (X-Pro or X-Hyp) to X+Pro or X+Hyp. Prolidase deficiency is a rare autosomal recessive disease characterized by chronic ulcerative dermatitis and mental retardation. These patients excrete large amounts of iminodipeptides containing C-terminal proline in the urine due to hereditary prolidase deficiency (PMID: 12636053 , 11863289 , 2387877 , 1874885 , 9586797 ).
Structure
Data?1582752400
Synonyms
ValueSource
L-Pro-L-hypChEBI
L-Prolyl-L-hydroxyprolineChEBI
(4R)-L-Prolyl-4-hydroxy-L-prolineHMDB
4-Hydroxy-1-L-prolyl-prolineHMDB
L-4-Hydroxy-1-L-prolyl-prolineHMDB
Proline-hydroxyprolineHMDB
trans-4-Hydroxy-1-L-prolyl-prolineHMDB
ProlylhydroxyprolineChEBI
Pro-hydroxy-ProHMDB
Pro-HypHMDB
Proline hydroxyproline dipeptideHMDB
Proline-hydroxyproline dipeptideHMDB
Chemical FormulaC10H16N2O4
Average Molecular Weight228.245
Monoisotopic Molecular Weight228.11100701
IUPAC Name(2S,4R)-4-hydroxy-1-[(2S)-pyrrolidine-2-carbonyl]pyrrolidine-2-carboxylic acid
Traditional Nameproline-hydroxyproline
CAS Registry Number18684-24-7
SMILES
O[C@@H]1C[C@H](N(C1)C(=O)[C@@H]1CCCN1)C(O)=O
InChI Identifier
InChI=1S/C10H16N2O4/c13-6-4-8(10(15)16)12(5-6)9(14)7-2-1-3-11-7/h6-8,11,13H,1-5H2,(H,15,16)/t6-,7+,8+/m1/s1
InChI KeyONPXCLZMBSJLSP-CSMHCCOUSA-N
Chemical Taxonomy
Description Belongs to the class of organic compounds known as dipeptides. These are organic compounds containing a sequence of exactly two alpha-amino acids joined by a peptide bond.
KingdomOrganic compounds
Super ClassOrganic acids and derivatives
ClassCarboxylic acids and derivatives
Sub ClassAmino acids, peptides, and analogues
Direct ParentDipeptides
Alternative Parents
Substituents
  • Alpha-dipeptide
  • N-acyl-alpha-amino acid
  • N-acyl-alpha amino acid or derivatives
  • Proline or derivatives
  • N-acyl-l-alpha-amino acid
  • Alpha-amino acid amide
  • Alpha-amino acid or derivatives
  • N-acylpyrrolidine
  • Pyrrolidine carboxylic acid
  • Pyrrolidine carboxylic acid or derivatives
  • Pyrrolidine-2-carboxamide
  • Tertiary carboxylic acid amide
  • Pyrrolidine
  • Secondary alcohol
  • Amino acid
  • Amino acid or derivatives
  • Carboxamide group
  • Secondary amine
  • Azacycle
  • Organoheterocyclic compound
  • Carboxylic acid
  • Secondary aliphatic amine
  • Monocarboxylic acid or derivatives
  • Hydrocarbon derivative
  • Organopnictogen compound
  • Organic oxide
  • Alcohol
  • Organonitrogen compound
  • Carbonyl group
  • Organooxygen compound
  • Amine
  • Organic nitrogen compound
  • Organic oxygen compound
  • Aliphatic heteromonocyclic compound
Molecular FrameworkAliphatic heteromonocyclic compounds
External Descriptors
Ontology
Physiological effectNot Available
Disposition
ProcessNot Available
Role
Physical Properties
StateSolid
Experimental Molecular Properties
PropertyValueReference
Melting PointNot AvailableNot Available
Boiling PointNot AvailableNot Available
Water SolubilityNot AvailableNot Available
LogPNot AvailableNot Available
Experimental Chromatographic PropertiesNot Available
Predicted Molecular Properties
PropertyValueSource
Water Solubility109 g/LALOGPS
logP-4ChemAxon
pKa (Strongest Acidic)3.54ChemAxon
pKa (Strongest Basic)9.82ChemAxon
Physiological Charge0ChemAxon
Hydrogen Acceptor Count5ChemAxon
Hydrogen Donor Count3ChemAxon
Polar Surface Area89.87 ŲChemAxon
Rotatable Bond Count2ChemAxon
Refractivity54.37 m³·mol⁻¹ChemAxon
Polarizability22.32 ųChemAxon
Number of Rings2ChemAxon
BioavailabilityYesChemAxon
Rule of FiveYesChemAxon
Ghose FilterNoChemAxon
Veber's RuleNoChemAxon
MDDR-like RuleNoChemAxon
Predicted Chromatographic Properties

Predicted Collision Cross Sections

PredictorAdduct TypeCCS Value (Å2)Reference
DarkChem[M+H]+151.27231661259
DarkChem[M-H]-150.29131661259
DeepCCS[M+H]+150.37330932474
DeepCCS[M-H]-147.97830932474
DeepCCS[M-2H]-181.04230932474
DeepCCS[M+Na]+156.28630932474
AllCCS[M+H]+151.132859911
AllCCS[M+H-H2O]+147.332859911
AllCCS[M+NH4]+154.732859911
AllCCS[M+Na]+155.732859911
AllCCS[M-H]-150.432859911
AllCCS[M+Na-2H]-150.332859911
AllCCS[M+HCOO]-150.432859911

Predicted Kovats Retention Indices

Underivatized

MetaboliteSMILESKovats RI ValueColumn TypeReference
ProlylhydroxyprolineO[C@@H]1C[C@H](N(C1)C(=O)[C@@H]1CCCN1)C(O)=O3401.2Standard polar33892256
ProlylhydroxyprolineO[C@@H]1C[C@H](N(C1)C(=O)[C@@H]1CCCN1)C(O)=O2172.6Standard non polar33892256
ProlylhydroxyprolineO[C@@H]1C[C@H](N(C1)C(=O)[C@@H]1CCCN1)C(O)=O2268.2Semi standard non polar33892256

Derivatized

Derivative Name / StructureSMILESKovats RI ValueColumn TypeReference
Prolylhydroxyproline,1TMS,isomer #1C[Si](C)(C)O[C@@H]1C[C@@H](C(=O)O)N(C(=O)[C@@H]2CCCN2)C12141.1Semi standard non polar33892256
Prolylhydroxyproline,1TMS,isomer #2C[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O)CN1C(=O)[C@@H]1CCCN12078.7Semi standard non polar33892256
Prolylhydroxyproline,1TMS,isomer #3C[Si](C)(C)N1CCC[C@H]1C(=O)N1C[C@H](O)C[C@H]1C(=O)O2036.4Semi standard non polar33892256
Prolylhydroxyproline,2TMS,isomer #1C[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C)CN1C(=O)[C@@H]1CCCN12144.4Semi standard non polar33892256
Prolylhydroxyproline,2TMS,isomer #2C[Si](C)(C)O[C@@H]1C[C@@H](C(=O)O)N(C(=O)[C@@H]2CCCN2[Si](C)(C)C)C12084.6Semi standard non polar33892256
Prolylhydroxyproline,2TMS,isomer #3C[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C2062.6Semi standard non polar33892256
Prolylhydroxyproline,3TMS,isomer #1C[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C2152.3Semi standard non polar33892256
Prolylhydroxyproline,3TMS,isomer #1C[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C2224.4Standard non polar33892256
Prolylhydroxyproline,3TMS,isomer #1C[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C2678.3Standard polar33892256
Prolylhydroxyproline,1TBDMS,isomer #1CC(C)(C)[Si](C)(C)O[C@@H]1C[C@@H](C(=O)O)N(C(=O)[C@@H]2CCCN2)C12372.8Semi standard non polar33892256
Prolylhydroxyproline,1TBDMS,isomer #2CC(C)(C)[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O)CN1C(=O)[C@@H]1CCCN12332.0Semi standard non polar33892256
Prolylhydroxyproline,1TBDMS,isomer #3CC(C)(C)[Si](C)(C)N1CCC[C@H]1C(=O)N1C[C@H](O)C[C@H]1C(=O)O2303.9Semi standard non polar33892256
Prolylhydroxyproline,2TBDMS,isomer #1CC(C)(C)[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C(C)(C)C)CN1C(=O)[C@@H]1CCCN12599.9Semi standard non polar33892256
Prolylhydroxyproline,2TBDMS,isomer #2CC(C)(C)[Si](C)(C)O[C@@H]1C[C@@H](C(=O)O)N(C(=O)[C@@H]2CCCN2[Si](C)(C)C(C)(C)C)C12582.5Semi standard non polar33892256
Prolylhydroxyproline,2TBDMS,isomer #3CC(C)(C)[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C(C)(C)C2546.4Semi standard non polar33892256
Prolylhydroxyproline,3TBDMS,isomer #1CC(C)(C)[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C(C)(C)C)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C(C)(C)C2830.1Semi standard non polar33892256
Prolylhydroxyproline,3TBDMS,isomer #1CC(C)(C)[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C(C)(C)C)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C(C)(C)C2799.3Standard non polar33892256
Prolylhydroxyproline,3TBDMS,isomer #1CC(C)(C)[Si](C)(C)OC(=O)[C@@H]1C[C@@H](O[Si](C)(C)C(C)(C)C)CN1C(=O)[C@@H]1CCCN1[Si](C)(C)C(C)(C)C2970.4Standard polar33892256
Spectra

GC-MS Spectra

Spectrum TypeDescriptionSplash KeyDeposition DateSourceView
Predicted GC-MSPredicted GC-MS Spectrum - Prolylhydroxyproline GC-MS (Non-derivatized) - 70eV, Positivesplash10-00dj-9200000000-cefb6332c4f93d2283b32017-09-01Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - Prolylhydroxyproline GC-MS (2 TMS) - 70eV, Positivesplash10-0a4l-2692000000-7b1c4c7371558705bfb02017-10-06Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - Prolylhydroxyproline GC-MS (Non-derivatized) - 70eV, PositiveNot Available2021-10-12Wishart LabView Spectrum
Predicted GC-MSPredicted GC-MS Spectrum - Prolylhydroxyproline GC-MS (Non-derivatized) - 70eV, PositiveNot Available2021-10-12Wishart LabView Spectrum

MS/MS Spectra

Spectrum TypeDescriptionSplash KeyDeposition DateSourceView
Experimental LC-MS/MSLC-MS/MS Spectrum - Prolylhydroxyproline 35V, Positive-QTOFsplash10-00di-9200000000-6af4dc9ae133d399503c2021-09-20HMDB team, MONAView Spectrum
Experimental LC-MS/MSLC-MS/MS Spectrum - Prolylhydroxyproline 35V, Negative-QTOFsplash10-0b90-2900000000-84bcb537803c3e383c982021-09-20HMDB team, MONAView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 10V, Positive-QTOFsplash10-03di-1490000000-d607eb5709327adc37c32016-06-03Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 20V, Positive-QTOFsplash10-0229-9520000000-53efc51e1a53a9bb992e2016-06-03Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 40V, Positive-QTOFsplash10-00di-9200000000-c54979309cb483b471432016-06-03Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 10V, Negative-QTOFsplash10-0059-0690000000-385af9502303330863e32016-08-03Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 20V, Negative-QTOFsplash10-05o0-3920000000-648587bfd6a99e5a6a252016-08-03Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 40V, Negative-QTOFsplash10-0239-9200000000-e801efd4fdf93e14e8f22016-08-03Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 10V, Negative-QTOFsplash10-01u1-4890000000-317a4ceb981d4c1d3a2c2021-09-22Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 20V, Negative-QTOFsplash10-03di-2900000000-cb814d27ee81988485472021-09-22Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 40V, Negative-QTOFsplash10-0006-9100000000-df69d58c4ec35c77f0112021-09-22Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 10V, Positive-QTOFsplash10-01t9-5690000000-afc10370af26972ee32d2021-09-23Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 20V, Positive-QTOFsplash10-0229-9610000000-4039cba60bbe790e2e1c2021-09-23Wishart LabView Spectrum
Predicted LC-MS/MSPredicted LC-MS/MS Spectrum - Prolylhydroxyproline 40V, Positive-QTOFsplash10-00di-9300000000-0dd3ad4a047284fe2d792021-09-23Wishart LabView Spectrum

NMR Spectra

Spectrum TypeDescriptionDeposition DateSourceView
Predicted 1D NMR1H NMR Spectrum (1D, 100 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 100 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 1000 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 1000 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 200 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 200 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 300 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 300 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 400 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 400 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 500 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 500 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 600 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 600 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 700 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 700 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 800 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 800 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR1H NMR Spectrum (1D, 900 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Predicted 1D NMR13C NMR Spectrum (1D, 900 MHz, D2O, predicted)2021-09-29Wishart LabView Spectrum
Biological Properties
Cellular LocationsNot Available
Biospecimen Locations
  • Blood
  • Cerebrospinal Fluid (CSF)
  • Sweat
  • Urine
Tissue Locations
  • Placenta
Pathways
Normal Concentrations
BiospecimenStatusValueAgeSexConditionReferenceDetails
BloodExpected but not QuantifiedNot QuantifiedNot SpecifiedNot SpecifiedNormal details
Cerebrospinal Fluid (CSF)Detected and Quantified0.87 +/- 1.0 uMAdult (>18 years old)BothNormal details
UrineDetected and Quantified4.8-9.4 umol/mmol creatinineAdult (>18 years old)FemaleNormal details
UrineDetected and Quantified4.5-7.7 umol/mmol creatinineAdult (>18 years old)MaleNormal details
UrineDetected and Quantified2.4-25.6 umol/mmol creatinineAdult (>18 years old)BothNormal details
Abnormal Concentrations
BiospecimenStatusValueAgeSexConditionReferenceDetails
Cerebrospinal Fluid (CSF)Detected and Quantified0.086 +/- 0.016 uMAdult (>18 years old)BothAlzheimer's disease details
SweatDetected but not QuantifiedNot QuantifiedInfant (0-1 year old)Not Specifiedscreen-positive CF details
UrineDetected but not QuantifiedNot QuantifiedAdult (>18 years old)FemaleEpithelial ovarian cancer details
Associated Disorders and Diseases
Disease References
Alzheimer's disease
  1. Fonteh AN, Harrington RJ, Tsai A, Liao P, Harrington MG: Free amino acid and dipeptide changes in the body fluids from Alzheimer's disease subjects. Amino Acids. 2007 Feb;32(2):213-24. Epub 2006 Oct 10. [PubMed:17031479 ]
Cystic fibrosis
  1. Adriana Nori de Macedo. Robust capillary electrophoresis methods for biomarker discovery and routine measurements in clinical and epidemiological applications. March 2017 [Link]
Associated OMIM IDs
DrugBank IDNot Available
Phenol Explorer Compound IDNot Available
FooDB IDFDB024028
KNApSAcK IDNot Available
Chemspider ID10077215
KEGG Compound IDNot Available
BioCyc IDNot Available
BiGG IDNot Available
Wikipedia LinkNot Available
METLIN IDNot Available
PubChem Compound11902892
PDB IDNot Available
ChEBI ID74767
Food Biomarker OntologyNot Available
VMH IDNot Available
MarkerDB IDMDB00000488
Good Scents IDNot Available
References
Synthesis Referenceustova, V.; Blaha, Karel. Amino acids and peptides. CXXVI. Dipeptides containing proline and 4-hydroxyproline. Collection of Czechoslovak Chemical Communications (1975), 40(3), 662-9.
Material Safety Data Sheet (MSDS)Not Available
General References
  1. Husek P, Pohlidal A, Slabik D: Rapid screening of urinary proline-hydroxyproline dipeptide in bone turnover studies. J Chromatogr B Analyt Technol Biomed Life Sci. 2002 Feb 5;767(1):169-74. [PubMed:11863289 ]
  2. Pohlidal A, Husek P, Palicka V, Slabik D, Hill M, Matucha P: Novel and traditional biomarkers of bone turnover in postmenopausal women. Clin Chem Lab Med. 2003 Jan;41(1):74-8. [PubMed:12636053 ]
  3. Sugahara K, Kodama H: Liquid chromatography-mass spectrometry for simultaneous analyses of iminodipeptides containing an N-terminal or a C-terminal proline. J Chromatogr. 1991 Apr 19;565(1-2):408-15. [PubMed:1874885 ]
  4. Kodama H, Nakamura H, Sugahara K, Numajiri Y: Liquid chromatography-mass spectrometry for the qualitative analyses of iminodipeptides in the urine of patients with prolidase deficiency. J Chromatogr. 1990 May 18;527(2):279-88. [PubMed:2387877 ]
  5. Zhang J, Sugahara K, Yasuda K, Kodama H, Sagara Y, Kodama H: The effects of serum iminodipeptides and prednisolone on superoxide generation and tyrosyl phosphorylation of proteins in neutrophils from a patient with prolidase deficiency. Free Radic Biol Med. 1998 Mar 15;24(5):689-98. [PubMed:9586797 ]
  6. Lowry M, Hall DE, Brosnan JT: Metabolism of glycine- and hydroxyproline-containing peptides by the isolated perfused rat kidney. Biochem J. 1985 Jul 15;229(2):545-9. [PubMed:4038280 ]
  7. Kawaguchi T, Nanbu PN, Kurokawa M: Distribution of prolylhydroxyproline and its metabolites after oral administration in rats. Biol Pharm Bull. 2012;35(3):422-7. [PubMed:22382331 ]
  8. Lampiaho K, Nikkari T, Pikkarainen J, Karkkainen J, Kulonen E: Unexpected occurrence of prolylhydroxyproline during the analysis of collagen-bound carbohydrates by gas-liquid chromatography. J Chromatogr. 1972 Feb 2;64(2):211-8. [PubMed:5013106 ]
  9. Bienenstock HKIBRICK AC: Urinary excretion of prolylhydroxyproline in rheumatic diseases. Ann Rheum Dis. 1969 Jan;28(1):28-30. [PubMed:5305862 ]
  10. Codini M, Palmerini CA, Fini C, Lucarelli C, Floridi A: High-performance liquid chromatographic method for the determination of prolyl peptides in urine. J Chromatogr. 1991 Jan 4;536(1-2):337-41. [PubMed:2050773 ]
  11. KIBRICK AC, HASHIRO CQ, SCHULTZ RS, WALTERS MI, MILHORAT AT: PROLYLHYDROXYPROLINE IN URINE: ITS DETERMINATION AND OBSERVATIONS IN MUSCULAR DYSTROPHY. Clin Chim Acta. 1964 Oct;10:344-51. [PubMed:14219579 ]
  12. Hueckel HJ, Rogers QR: Prolylhydroxyproline absorption in hamsters. Can J Biochem. 1972 Jul;50(7):782-90. [PubMed:5050935 ]
  13. Kibrick AC, Power HL, Sevendal E, Milhorat AT: Prolylhydroxyproline in urine: improved method for detecting radioactivity with a scanner on full sheets of chromatography paper. Anal Biochem. 1968 Oct 24;25(1):40-5. [PubMed:5704756 ]
  14. KIBRICK AC, HASHIRO CQ, WALTERS MI, MILHORAT AT: DIKETOPIPERAZINE OF PROLYLHYDROXYPROLINE IN NORMAL HUMAN URINE. Proc Soc Exp Biol Med. 1965 Jan;118:62-4. [PubMed:14254586 ]
  15. Zhang A, Sun H, Han Y, Yuan Y, Wang P, Song G, Yuan X, Zhang M, Xie N, Wang X: Exploratory urinary metabolic biomarkers and pathways using UPLC-Q-TOF-HDMS coupled with pattern recognition approach. Analyst. 2012 Sep 21;137(18):4200-8. doi: 10.1039/c2an35780a. Epub 2012 Jul 31. [PubMed:22852134 ]
  16. Elshenawy S, Pinney SE, Stuart T, Doulias PT, Zura G, Parry S, Elovitz MA, Bennett MJ, Bansal A, Strauss JF 3rd, Ischiropoulos H, Simmons RA: The Metabolomic Signature of the Placenta in Spontaneous Preterm Birth. Int J Mol Sci. 2020 Feb 4;21(3). pii: ijms21031043. doi: 10.3390/ijms21031043. [PubMed:32033212 ]