Exact Mass: 181.1340812
Exact Mass Matches: 181.1340812
Found 412 metabolites which its exact mass value is equals to given mass value 181.1340812,
within given mass tolerance error 0.05 dalton. Try search metabolite list with more accurate mass tolerance error
0.01 dalton.
Pyridostigmine
C9H13N2O2+ (181.09769780000002)
Pyridostigmine is only found in individuals that have used or taken this drug. It is a cholinesterase inhibitor with a slightly longer duration of action than neostigmine. It is used in the treatment of myasthenia gravis and to reverse the actions of muscle relaxants. [PubChem]Pyridostigmine inhibits acetylcholinesterase in the synaptic cleft by competing with acetylcholine for attachment to acetylcholinesterase, thus slowing down the hydrolysis of acetylcholine, and thereby increases efficiency of cholinergic transmission in the neuromuscular junction and prolonges the effects of acetylcholine. N - Nervous system > N07 - Other nervous system drugs > N07A - Parasympathomimetics > N07AA - Anticholinesterases D018377 - Neurotransmitter Agents > D018678 - Cholinergic Agents > D002800 - Cholinesterase Inhibitors C471 - Enzyme Inhibitor > C47792 - Acetylcholinesterase Inhibitor D004791 - Enzyme Inhibitors
Dicyclohexylamine
INTERNAL_ID 2356; CONFIDENCE Reference Standard (Level 1) CONFIDENCE Reference Standard (Level 1); INTERNAL_ID 2356 D004791 - Enzyme Inhibitors
Acetylcholine chloride
C7H16ClNO2 (181.08695060000002)
D018377 - Neurotransmitter Agents > D018678 - Cholinergic Agents > D018679 - Cholinergic Agonists C78272 - Agent Affecting Nervous System > C47796 - Cholinergic Agonist D002317 - Cardiovascular Agents > D014665 - Vasodilator Agents Acetylcholine chloride (ACh chloride), a neurotransmitter, is a potent cholinergic agonist. Acetylcholine chloride is a modulator of the activity of dopaminergic (DAergic) neurons through the stimulation of nicotinic acetylcholine receptors (nAChRs)[1][2]. Acetylcholine chloride inhibits p53 mutant peptide aggregation in vitro[5]. Acetylcholine chloride (ACh chloride), a neurotransmitter, is a potent cholinergic agonist. Acetylcholine chloride is a modulator of the activity of dopaminergic (DAergic) neurons through the stimulation of nicotinic acetylcholine receptors (nAChRs)[1][2]. Acetylcholine chloride inhibits p53 mutant peptide aggregation in vitro[5].
3,4-Dimethoxyphenylethylamine
3,4-Dimethoxyphenylethylamine, also known as 3,4-DMPEA or DMPEA is an endogenous metabolite found in urine that belongs to both the phenethylamine and catecholamine families. DMPEA is an analogue of dopamine (3,4-dihydroxyphenethylamine), with a substitution of the hydroxy groups with methoxy groups. DMPEA is also structurally similar to mescaline (3,4,5-trimethoxyphenylethylamine) and occurs naturally alongside it in various species of cacti such as the San Pedro and Peruvian Torch (PMID: 5511715, 925910, 600028). DMPEA received wide attention after it was proposed as a biomarker in schizophrenic patients urine, however later studies revealed that DMPEA is also excreted by non-schizophrenics (PMID: 709888). DMPEA has little known bioactivity, but it has some action as a monoamine oxidase inhibitor (PMID: 886445). DMPEA has also been shown to have neurotoxic effects, especially in the nigrostriatal system and among dopaminergic neurons (PMID: 9409711, 9134983). DMPEA appears to be an inhibitor of mitochondrial complex I (PMID: 9409711).
3-O-Methyl-a-methyldopamine
3-O-Methyl-a-methyldopamine is a metabolite of methyldopa. Methyldopa (-α-Methyl-3,4-dihydroxyphenylalanine; Aldomet, Aldoril, Dopamet, Dopegyt, etc. ) is an alpha-adrenergic agonist (selective for α2-adrenergic receptors) psychoactive drug used as a sympatholytic or antihypertensive. Its use is now mostly deprecated following the introduction of alternative safer classes of agents. However, it continues to have a role in otherwise difficult to treat hypertension and gestational hypertension (also known as pregnancy-induced hypertension). (Wikipedia)
beta-O-Methylynephrine
beta-O-Methylynephrine is found in citrus. beta-O-Methylynephrine is obtained from tangerine leaves, poss. as artifact. obtained from tangerine leaves, poss. as artifact. beta-O-Methylynephrine is found in citrus.
(R)-2-Nitro-p-mentha-1,5-diene
Constituent of Angelica archangelica (angelica). (R)-2-Nitro-p-mentha-1,5-diene is found in fats and oils, herbs and spices, and green vegetables. (R)-2-Nitro-p-mentha-1,5-diene is found in fats and oils. (R)-2-Nitro-p-mentha-1,5-diene is a constituent of Angelica archangelica (angelica)
cis-6-Nitro-p-mentha-1(7),2-diene
Constituent of Angelica archangelica (angelica). cis-6-Nitro-p-mentha-1(7),2-diene is found in fats and oils, herbs and spices, and green vegetables. trans-6-Nitro-p-mentha-1(7),2-dien is found in fats and oils. trans-6-Nitro-p-mentha-1(7),2-dien is a constituent of Angelica archangelica (angelica)
6-Methyltetrahydropterin
Cofactor of phenylalanine and tyrosine hydroxylase (S-form) (Combined Chemical Dictionary) [HMDB] Cofactor of phenylalanine and tyrosine hydroxylase (S-form) (Combined Chemical Dictionary).
N-Ethyl trans-2-cis-6-nonadienamide
N-Ethyl trans-2-cis-6-nonadienamide is used as a food additive [EAFUS] ("EAFUS: Everything Added to Food in the United States. [http://www.eafus.com/]") It is used as a food additive .
5-Ethyl-4-methyl-2-pentyloxazole
5-Ethyl-4-methyl-2-pentyloxazole is found in potato. 5-Ethyl-4-methyl-2-pentyloxazole is a constituent of French fries. Constituent of French fries. 5-Ethyl-4-methyl-2-pentyloxazole is found in potato.
4-Hexyl-2,5-dimethyloxazole
4-Hexyl-2,5-dimethyloxazole is found in animal foods. 4-Hexyl-2,5-dimethyloxazole is a constituent of roast beef. Constituent of roast beef. 4-Hexyl-2,5-dimethyloxazole is found in animal foods.
2-Butyl-4,5-diethyloxazole
2-Butyl-4,5-diethyloxazole is found in potato. 2-Butyl-4,5-diethyloxazole is a constituent of French fries. Constituent of French fries. 2-Butyl-4,5-diethyloxazole is found in potato.
2-Butyl-5-methyl-4-propyloxazole
2-Butyl-5-methyl-4-propyloxazole is found in potato. 2-Butyl-5-methyl-4-propyloxazole is a constituent of French fries. Constituent of French fries. 2-Butyl-5-methyl-4-propyloxazole is found in potato.
2-Hexyl-4,5-dimethyloxazole
2-Hexyl-4,5-dimethyloxazole is found in potato. 2-Hexyl-4,5-dimethyloxazole is a constituent of French fried potato. Constituent of French fried potato. 2-Hexyl-4,5-dimethyloxazole is found in potato.
5-Butyl-4-methyl-2-propyloxazole
Not reported in nature. Not reported in nature
4-Ethyl-5-methyl-2-pentyloxazol
Not reported in nature. Not reported in nature
2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone
2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone is found in alcoholic beverages. Proline-derived Maillard product. 2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone is a flavouring agent. 2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone is a constituent of dark malt. Proline-derived Maillard product. Flavouring agent. Constituent of dark malt. 2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone is found in alcoholic beverages and cereals and cereal products.
2-(5-Methyl-2-furanyl)-3-piperidinol
Proline-derived Maillard product. Proline-derived Maillard product
5-(1-Pyrrolidinylmethyl)-2-furanmethanol
Proline-derived Maillard product. Proline-derived Maillard product
2-Aminofluorene
D009676 - Noxae > D002273 - Carcinogens D009676 - Noxae > D009153 - Mutagens
Azepexole
C78272 - Agent Affecting Nervous System > C29747 - Adrenergic Agent > C87053 - Adrenergic Agonist D018377 - Neurotransmitter Agents > D018663 - Adrenergic Agents > D000322 - Adrenergic Agonists D002317 - Cardiovascular Agents > D000959 - Antihypertensive Agents D002317 - Cardiovascular Agents > D014662 - Vasoconstrictor Agents
Etilefrine
C - Cardiovascular system > C01 - Cardiac therapy > C01C - Cardiac stimulants excl. cardiac glycosides > C01CA - Adrenergic and dopaminergic agents D018373 - Peripheral Nervous System Agents > D001337 - Autonomic Agents > D013566 - Sympathomimetics D018377 - Neurotransmitter Agents > D018663 - Adrenergic Agents > D000322 - Adrenergic Agonists C78272 - Agent Affecting Nervous System > C29747 - Adrenergic Agent D002317 - Cardiovascular Agents > D014662 - Vasoconstrictor Agents D020011 - Protective Agents > D002316 - Cardiotonic Agents
2-Amino-6-methyl-2,3,6,7-tetrahydro-1H-pteridin-4-one
5-[(2R)-2-Aminopropyl]cyclohexa-1,5-diene-1-carboxylic acid
1,2,3-Trimethoxy-5-ethylbenzene
1,2,3-trimethoxy-5-ethylbenzene is slightly soluble (in water) and an extremely weak basic (essentially neutral) compound (based on its pKa). 1,2,3-trimethoxy-5-ethylbenzene can be found in tea, which makes 1,2,3-trimethoxy-5-ethylbenzene a potential biomarker for the consumption of this food product.
Methylgeranate
C11H17O2- (181.12284820000002)
Methylgeranate is also known as methylgeranic acid. Methylgeranate is slightly soluble (in water) and a very weakly acidic compound (based on its pKa). Methylgeranate can be found in papaya, which makes methylgeranate a potential biomarker for the consumption of this food product.
3-Methylcarbazole
3-Methylcarbazole is an carbazole alkaloid compound with anticancer effects. 3-Methylcarbazole shows growth inhibitory activity (IC50 of 25 μg/mL) on human fibrosarcoma HT-1080 cells[1]. 3-Methylcarbazole is an carbazole alkaloid compound with anticancer effects. 3-Methylcarbazole shows growth inhibitory activity (IC50 of 25 μg/mL) on human fibrosarcoma HT-1080 cells[1].
(R)-Methyl-5-(1-methylethyl)-1-nitro-1,3-cyclohexadiene
(4S-trans)-3-Methylene-6-(1-methylethyl)-4-nitrocyclohexene
N-Phenyldiethanolamine
CONFIDENCE standard compound; INTERNAL_ID 1287; DATASET 20200303_ENTACT_RP_MIX504; DATA_PROCESSING MERGING RMBmix ver. 0.2.7; DATA_PROCESSING PRESCREENING Shinyscreen ver. 0.8.0; ORIGINAL_ACQUISITION_NO 3514; ORIGINAL_PRECURSOR_SCAN_NO 3513 CONFIDENCE standard compound; INTERNAL_ID 1287; DATASET 20200303_ENTACT_RP_MIX504; DATA_PROCESSING MERGING RMBmix ver. 0.2.7; DATA_PROCESSING PRESCREENING Shinyscreen ver. 0.8.0; ORIGINAL_ACQUISITION_NO 3512; ORIGINAL_PRECURSOR_SCAN_NO 3507 CONFIDENCE standard compound; INTERNAL_ID 1287; DATASET 20200303_ENTACT_RP_MIX504; DATA_PROCESSING MERGING RMBmix ver. 0.2.7; DATA_PROCESSING PRESCREENING Shinyscreen ver. 0.8.0; ORIGINAL_ACQUISITION_NO 3538; ORIGINAL_PRECURSOR_SCAN_NO 3536 CONFIDENCE standard compound; INTERNAL_ID 1287; DATASET 20200303_ENTACT_RP_MIX504; DATA_PROCESSING MERGING RMBmix ver. 0.2.7; DATA_PROCESSING PRESCREENING Shinyscreen ver. 0.8.0; ORIGINAL_ACQUISITION_NO 3529; ORIGINAL_PRECURSOR_SCAN_NO 3527 CONFIDENCE standard compound; INTERNAL_ID 1287; DATASET 20200303_ENTACT_RP_MIX504; DATA_PROCESSING MERGING RMBmix ver. 0.2.7; DATA_PROCESSING PRESCREENING Shinyscreen ver. 0.8.0; ORIGINAL_ACQUISITION_NO 3560; ORIGINAL_PRECURSOR_SCAN_NO 3557 CONFIDENCE standard compound; INTERNAL_ID 1287; DATASET 20200303_ENTACT_RP_MIX504; DATA_PROCESSING MERGING RMBmix ver. 0.2.7; DATA_PROCESSING PRESCREENING Shinyscreen ver. 0.8.0; ORIGINAL_ACQUISITION_NO 3523; ORIGINAL_PRECURSOR_SCAN_NO 3520
4-Methylthioamphetamine
D002491 - Central Nervous System Agents > D000697 - Central Nervous System Stimulants
Etilefrin
C - Cardiovascular system > C01 - Cardiac therapy > C01C - Cardiac stimulants excl. cardiac glycosides > C01CA - Adrenergic and dopaminergic agents D018373 - Peripheral Nervous System Agents > D001337 - Autonomic Agents > D013566 - Sympathomimetics D018377 - Neurotransmitter Agents > D018663 - Adrenergic Agents > D000322 - Adrenergic Agonists C78272 - Agent Affecting Nervous System > C29747 - Adrenergic Agent D002317 - Cardiovascular Agents > D014662 - Vasoconstrictor Agents D020011 - Protective Agents > D002316 - Cardiotonic Agents CONFIDENCE Reference Standard (Level 1); HBM4EU - science and policy for a healthy future (https://www.hbm4eu.eu) HBM4EU - science and policy for a healthy future (https://www.hbm4eu.eu); CONFIDENCE Reference Standard (Level 1)
N-Di-Me,Et ester-2-Aminoethylphosphonic acid
C6H16NO3P (181.08677559999998)
(S)-5-(1-hydroxybutyl)-6-methylpyridin-2(1H)-one|chrysogedone A
3-Methylcarbazole
3-Methyl-9H-carbazole is a natural product found in Murraya euchrestifolia, Clausena heptaphylla, and other organisms with data available. 3-Methylcarbazole is an carbazole alkaloid compound with anticancer effects. 3-Methylcarbazole shows growth inhibitory activity (IC50 of 25 μg/mL) on human fibrosarcoma HT-1080 cells[1]. 3-Methylcarbazole is an carbazole alkaloid compound with anticancer effects. 3-Methylcarbazole shows growth inhibitory activity (IC50 of 25 μg/mL) on human fibrosarcoma HT-1080 cells[1].
2-Hepten-4-yn-1-amine, N,6,6-trimethyl-, (E)- Metabolite
5-(Dimethylamino)-pentanoic acid hydrochloride
C7H16ClNO2 (181.08695060000002)
Piperazine,1-[(3-methyl-5-isoxazolyl)methyl]- (9CI)
BENZENEPROPANAMIDE, A-AMINO-N-[(1R)-1-[(3AS,4S,6S,7AR)-HEXAHYDRO-3A,5,5-TRIMETHYL-4,6-METHANO-1,3,2-BENZODIOXABOROL-2-YL]-3-METHYLBUTYL]-,HYDROCHLORIDE (1:1), (AS)
L-beta-Homoisoleucine hydrochloride
C7H16ClNO2 (181.08695060000002)
2,2-Difluoro-3-(Methylamino)propanoic Acid Hydrochloride
Methyl 5,6,7,8-tetrahydroimidazo[1,2-a]pyrazine-2-carboxylate
(1R,2R,4R)-2-Azido-1-isopropyl-4-methylcyclohexane
(R)-N,N-DIMETHYL-1-[(S)-1,2-BIS(DIPHENYLPHOSPHINO)FERROCENYL]ETHYLAMINE
TRANS-(4S,6S)-5,6-DIHYDRO-6-METHYL-4H-THIENO[2,3-B]THIOPYRAN-4-OL,7,7-DIOXIDE
tert-Butyl N-methylglycinate hydrochloride (1:1)
C7H16ClNO2 (181.08695060000002)
3-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)propanenitrile
dl-valine ethyl ester hydrochloride
C7H16ClNO2 (181.08695060000002)
2,4-DIMETHYL-1,4-DIHYDRO-PYRIDINE-3-CARBOXYLIC ACID ETHYL ESTER
Hexapropymate
N - Nervous system > N05 - Psycholeptics > N05C - Hypnotics and sedatives C78272 - Agent Affecting Nervous System > C29756 - Sedative and Hypnotic
1-ISOPROPYL-2,5-DIMETHYL-1H-PYRROLE-3-CARBOXYLIC ACID
5-Pyrimidinecarboxylicacid, 4-amino-2-methyl-, ethyl ester
Ethyl 3-Amino-2,2-dimethylpropanoate Hydrochloride
C7H16ClNO2 (181.08695060000002)
Methyl 6-aminohexanoate hydrochloride
C7H16ClNO2 (181.08695060000002)
Benzenemethanamine, 2,5-dimethoxy-a-methyl-, (aR)-
Benzenemethanamine, 2,6-dimethoxy-α-methyl-, (S)- (9CI)
3-(tert-butylamino)propanoic acid,hydrochloride
C7H16ClNO2 (181.08695060000002)
ETHYL 5-AMINOVALERATE HYDROCHLORIDE
C7H16ClNO2 (181.08695060000002)
5-amino-4-(methoxymethyl)-6-methyl-3-pyridinemethanamine
3-(DIETHYLAMINO)PROPANOIC ACID HYDROCHLORIDE
C7H16ClNO2 (181.08695060000002)
(1R,3R,4S)-Ethyl 3-aminobicyclo[2.2.1]hept-5-ene-2-carboxylate
(3-Carboxypropyl)trimethylammonium chloride
C7H16ClNO2 (181.08695060000002)
(3-Carboxypropyl)trimethylammonium chloride is angiopathic substance produced as an intermediary metabolite by gut microbiota that feed on carnitine in dietary red meat.
(3R-CIS)-(-)-2,3-DIHYDRO-3-ISOPROPYL-7A-METHYLPYRROLO-[2,1-B!OXAZOL-5(7AH)-ONE
(4-Methoxypiperidin-4-yl)methanol hydrochloride
C7H16ClNO2 (181.08695060000002)
tert-Butyl 2-aminopropanoate hydrochloride
C7H16ClNO2 (181.08695060000002)
Thieno[2,3-c]pyridine, 6-ethyl-4,5,6,7-tetrahydro-2-methyl- (9CI)
L-Alanine, butyl ester, hydrochloride
C7H16ClNO2 (181.08695060000002)
ethyl 2-(propan-2-ylamino)acetate,hydrochloride
C7H16ClNO2 (181.08695060000002)
Benzenemethanamine, 2,5-dimethoxy-α-methyl-, (αS)-
Methyl D-leucinate hydrochloride (1:1)
C7H16ClNO2 (181.08695060000002)
Methyl 4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylate
5-ACETYL-4-AMINO-2,6-DIMETHYL-2,3-DIHYDROPYRIDAZIN-3-ONE
N-Methyl-L-leucine hydrochloride (1:1)
C7H16ClNO2 (181.08695060000002)
Ethyl L-valinate hydrochloride (1:1)
C7H16ClNO2 (181.08695060000002)
(17B)-17-[(1-OXODODECYL)OXY]-ESTR-4-EN-3-ONE
C6H16NO3P (181.08677559999998)
(2a,6a,8a,9ab)-Hexahydro-8-hydroxy-2,6-methano-2H-quinolizin-3(4H)-one
pentyl 2-aminoacetate,hydrochloride
C7H16ClNO2 (181.08695060000002)
N-[(1,3,5-TRIMETHYL-1H-PYRAZOL-4-YL)METHYL]PROPAN-2-AMINE
(R)-1-(3,5-DIMETHOXYPHENYL)ETHANAMINE HYDROCHLORIDE
3-[Methyl-(1-methyl-piperidin-4-yl)-amino]-propionitrile
D-VALINE, 3-METHYL-, METHYL ESTER, HYDROCHLORIDE
C7H16ClNO2 (181.08695060000002)
2-(ethylamino)-6-methylpyrimidine-4-carboxylic acid
1-Methoxy-1-oxo-2-hexanaminium chloride
C7H16ClNO2 (181.08695060000002)
2-DIMETHYLAMINO-4-METHYL-PYRIMIDINE-5-CARBOXYLIC ACID
N-METHYL-N-[3-(1,3,5-TRIMETHYL-1H-PYRAZOL-4-YL)PROPYL]AMINE
Ethyl 3-amino-3-methylbutanoate hydrochloride
C7H16ClNO2 (181.08695060000002)
1H-Pyrrole-2-carboxylicacid, 3,4,5-trimethyl-, ethyl ester
7-Aminoheptanoic acid hydrochloride (1:1)
C7H16ClNO2 (181.08695060000002)
2-(5-AMINO(2-PYRIDYLOXY))ETHYL]DIMETHYLAMINE HYDROCHLORIDE SALT
1H-Pyrazol-3-amine,5-(4-methyl-1-piperazinyl)-(9CI)
Methyl 8-methyl-8-azabicyclo[3.2.1]oct-3-ene-4-carboxylate
Isohexylcyanoacrylate
D001697 - Biomedical and Dental Materials > D014014 - Tissue Adhesives
Chrysogedone A
A pyridone that is pyridin-2(1H)-one substituted by a methyl group at position 6 and a 1-hydroxybutyl group at position 5. It has been isolated from Penicillium chrysogenum.
Ethyl Hydrogen Diethylamidophosphate
C6H16NO3P (181.08677559999998)
AIDS-287167
3-Methylcarbazole is an carbazole alkaloid compound with anticancer effects. 3-Methylcarbazole shows growth inhibitory activity (IC50 of 25 μg/mL) on human fibrosarcoma HT-1080 cells[1]. 3-Methylcarbazole is an carbazole alkaloid compound with anticancer effects. 3-Methylcarbazole shows growth inhibitory activity (IC50 of 25 μg/mL) on human fibrosarcoma HT-1080 cells[1].
1,2,3-Trimethoxy-5-ethylbenzene
1,2,3-trimethoxy-5-ethylbenzene is slightly soluble (in water) and an extremely weak basic (essentially neutral) compound (based on its pKa). 1,2,3-trimethoxy-5-ethylbenzene can be found in tea, which makes 1,2,3-trimethoxy-5-ethylbenzene a potential biomarker for the consumption of this food product.
[(R)-2,2,3-trimethyl-2-oxocyclopent-3-en-1-yl]acetate
C10H13O3- (181.08646480000002)
5-[(2R)-2-Aminopropyl]cyclohexa-1,5-diene-1-carboxylic acid
5-Hydroxykynurenaminium(1+)
C9H13N2O2+ (181.09769780000002)
An ammonium ion that is the conjugate base of 5-hydroxykynurenamine, arising from selective protonation of the primary alkylamino function; major species at pH 7.3. COVID info from COVID-19 Disease Map Corona-virus Coronavirus SARS-CoV-2 COVID-19 SARS-CoV COVID19 SARS2 SARS
(2,2,3-Trimethyl-5-oxocyclopent-3-en-1-yl)acetate
C10H13O3- (181.08646480000002)
pyridostigmine
C9H13N2O2+ (181.09769780000002)
N - Nervous system > N07 - Other nervous system drugs > N07A - Parasympathomimetics > N07AA - Anticholinesterases D018377 - Neurotransmitter Agents > D018678 - Cholinergic Agents > D002800 - Cholinesterase Inhibitors C471 - Enzyme Inhibitor > C47792 - Acetylcholinesterase Inhibitor D004791 - Enzyme Inhibitors
3,4-Dimethoxyphenylethylamine
An aromatic ether that is the derivative of 2-phenylethylamine with methoxy substituents at the 3- and 4-positions. It is an alkaloid isolated from the Cactaceae family.
6-hydroxy-pseudooxy-nornicotinium
C9H13N2O2 (181.09769780000002)
A primary ammonium ion that is the conjugate acid of 6-hydroxy-pseudooxy-nornicotine resulting from the protonation of the primary amino group; major microspecies at pH 7.3.