SM(d17:1/20:4(6Z,8E,10E,14Z)-2OH(5S,12R))

(2-{[(2S,3R,4E)-2-[(5R,6Z,8E,10E,12S,14Z)-5,12-dihydroxyicosa-6,8,10,14-tetraenamido]-3-hydroxyheptadec-4-en-1-yl phosphono]oxy}ethyl)trimethylazanium

Formula: C42H77N2O8P (768.5417)
Chinese Name:
BioDeep ID: BioDeep_00000215361 ( View LC/MS Profile)
SMILES: [H][C@@](COP([O-])(=O)OCC[N+](C)(C)C)(NC(=O)CCC[C@@H](O)\C=C/C=C/C=C/[C@@H](O)C\C=C/CCCCC)[C@H](O)\C=C\CCCCCCCCCCCC



Found 68 Sample Hits

m/z Adducts Species Organ Scanning Sample
769.5502 [M+H]+
PPM:1.6
Mus musculus Urinary bladder MALDI (CHCA)
HR2MSI_mouse_urinary_bladder - S096 - PXD001283
Resolution: 10μm, 260x134

Description

Mass spectrometry imaging of phospholipids in mouse urinary bladder (imzML dataset)
The spatial distribution of phospholipids in a tissue section of mouse urinary bladder was analyzed by MALDI MS imaging at 10 micrometer pixel size with high mass resolution (using an LTQ Orbitrap mass spectrometer).

R, ö, mpp A, Guenther S, Schober Y, Schulz O, Takats Z, Kummer W, Spengler B, Histology by mass spectrometry: label-free tissue characterization obtained from high-accuracy bioanalytical imaging. Angew Chem Int Ed Engl, 49(22):3834-8(2010)

Fig. S2: Single ion images of compounds shown in Fig. 1A-B : (upper left to lower right) m/z = 743.5482 (unknown), m/z = 741.5307 (SM (16:0), [M+K]+), m/z = 798.5410 (PC (34:1), [M+K]+), m/z = 616.1767 (heme b, M+), m/z = 772.5253 (PC (32:0), [M+K]+).

Stability of determined mass values was in the range of +/- 1 ppm over 22 hours of measurement (Fig. S4), with a standard deviation of 0.56 ppm. Accuracy data were obtained during tissue scanning experiments by monitoring the mass signal at nominal mass 798. The internal lock mass function of the Orbitrap instrument was used for automatic calibration during imaging measurements, using the known matrix-related ion signals at m/z = 137.0233, m/z = 444.0925 and m/z = 716.1246.

769.5532 [M+H]+
PPM:5.5
Mus musculus Kidney MALDI (CHCA)
FULL_MS_centriod_CHCA_20210819 - FULL_MS_centriod_CHCA_20210819
Resolution: 17μm, 638x437

Description

AP-MALDI instrument demo test, mass spectrum scan in centroid mode.

807.6492 [M+K]+
PPM:12
Mus musculus Kidney MALDI (CHCA)
FULL_MS_centriod_CHCA_20210819 - FULL_MS_centriod_CHCA_20210819
Resolution: 17μm, 638x437

Description

AP-MALDI instrument demo test, mass spectrum scan in centroid mode.

769.556 [M+H]+
PPM:9.1
Homo sapiens Liver MALDI (DHB)
20171107_FIT4_DHBpos_p70_s50 - Rappez et al (2021) SpaceM reveals metabolic states of single cells
Resolution: 50μm, 70x70

Description

768.5627 [M-H2O+NH4]+
PPM:3
Rattus norvegicus Epididymis MALDI (DHB)
epik_dhb_head_ito08_43 - MTBLS58
Resolution: 17μm, 298x106

Description

768.5627 [M-H2O+NH4]+
PPM:3
Rattus norvegicus Epididymis MALDI (DHB)
epik_dhb_head_ito08_44 - MTBLS58
Resolution: 17μm, 299x111

Description

768.5623 [M-H2O+NH4]+
PPM:3.5
Rattus norvegicus Epididymis MALDI (DHB)
epik_dhb_head_ito08_46 - MTBLS58
Resolution: 17μm, 298x106

Description

768.5625 [M-H2O+NH4]+
PPM:3.2
Rattus norvegicus Epididymis MALDI (DHB)
epik_dhb_head_ito08_47 - MTBLS58
Resolution: 17μm, 301x111

Description

768.5622 [M-H2O+NH4]+
PPM:3.6
Rattus norvegicus Epididymis MALDI (DHB)
epik_dhb_head_ito08_48 - MTBLS58
Resolution: 17μm, 294x107

Description

768.5557 [M-H2O+NH4]+
PPM:12.1
Mus musculus Lung MALDI (DHB)
image3 - MTBLS2075
Resolution: 40μm, 146x190

Description

Fig. 4 MALDI-MSI data of mouse lung tissue after administration with D9-choline and U13C-DPPC–containing Poractant alfa surfactant (labels administered 12 h prior to tissue collection). Ion images of (A) m/z 796.6856 ([U13C-DPPC+Na]+), (B) m/z 756.5154 [PC32:0+Na]+), and (C) m/z 765.6079 ([D9-PC32:0+Na]+). D: Overlay image of [U13C-PC32:0+Na]+ (red) and [D9-PC32:0+Na]+ (green). Part-per-million (ppm) mass errors are indicated in parentheses. All images were visualized using total-ion-current normalization and using hotspot removal (high quantile = 99%). DPPC = PC16:0/16:0. MSI, mass spectrometry imaging; PC, phosphatidylcholine; U13C-DPPC, universally 13C-labeled dipalmitoyl PC.

769.5589 [M+H]+
PPM:12.9
Mus musculus Lung MALDI (DHB)
image3 - MTBLS2075
Resolution: 40μm, 146x190

Description

Fig. 4 MALDI-MSI data of mouse lung tissue after administration with D9-choline and U13C-DPPC–containing Poractant alfa surfactant (labels administered 12 h prior to tissue collection). Ion images of (A) m/z 796.6856 ([U13C-DPPC+Na]+), (B) m/z 756.5154 [PC32:0+Na]+), and (C) m/z 765.6079 ([D9-PC32:0+Na]+). D: Overlay image of [U13C-PC32:0+Na]+ (red) and [D9-PC32:0+Na]+ (green). Part-per-million (ppm) mass errors are indicated in parentheses. All images were visualized using total-ion-current normalization and using hotspot removal (high quantile = 99%). DPPC = PC16:0/16:0. MSI, mass spectrometry imaging; PC, phosphatidylcholine; U13C-DPPC, universally 13C-labeled dipalmitoyl PC.

768.5551 [M-H2O+NH4]+
PPM:12.9
Mus musculus Lung MALDI (DHB)
image4 - MTBLS2075
Resolution: 40μm, 162x156

Description

Fig 6c Fig. 6 MALDI-MSI of U13C-PC16:0/16:0 acyl chain remodeling. A: Averaged MALDI mass spectrum from lung tissue collected from mice euthanized 12 h after administration of D9-choline and U13C-DPPC–containing Poractant alfa surfactant. The ion at m/z 828.6321 is assigned as the [M+Na]+ ion of 13C24-PC16:0_20:4 formed by acyl remodeling of U13C-PC16:0/16:0. The “NL” value refers to the intensity of the base peak in the full range MS1 spectrum. B: MS/MS spectrum of precursor ions at m/z 828.5 ± 0.5 with fragment ions originating from [13C24-PC16:0_20:4+Na]+ annotated. Part-per-million (ppm) mass errors are provided in parentheses. C, D: MALDI-MSI data of [U13C-DPPC+Na]+ (blue), [PC36:4+Na]+ (green) and [13C24-PC16:0_20:4+Na]+ (red) in lung tissue collected from mice (C) 12 h and (D) 18 h after label administration. All images were visualized using total-ion-current normalization and hotspot removal (high quantile = 99%). MS/MS, tandem mass spectrometry; MSI, mass spectrometry imaging; PC, phosphatidylcholine; U13C-DPPC, universally 13C-labeled dipalmitoyl PC.

769.5567 [M+H]+
PPM:10
Mus musculus Lung MALDI (DHB)
image4 - MTBLS2075
Resolution: 40μm, 162x156

Description

Fig 6c Fig. 6 MALDI-MSI of U13C-PC16:0/16:0 acyl chain remodeling. A: Averaged MALDI mass spectrum from lung tissue collected from mice euthanized 12 h after administration of D9-choline and U13C-DPPC–containing Poractant alfa surfactant. The ion at m/z 828.6321 is assigned as the [M+Na]+ ion of 13C24-PC16:0_20:4 formed by acyl remodeling of U13C-PC16:0/16:0. The “NL” value refers to the intensity of the base peak in the full range MS1 spectrum. B: MS/MS spectrum of precursor ions at m/z 828.5 ± 0.5 with fragment ions originating from [13C24-PC16:0_20:4+Na]+ annotated. Part-per-million (ppm) mass errors are provided in parentheses. C, D: MALDI-MSI data of [U13C-DPPC+Na]+ (blue), [PC36:4+Na]+ (green) and [13C24-PC16:0_20:4+Na]+ (red) in lung tissue collected from mice (C) 12 h and (D) 18 h after label administration. All images were visualized using total-ion-current normalization and hotspot removal (high quantile = 99%). MS/MS, tandem mass spectrometry; MSI, mass spectrometry imaging; PC, phosphatidylcholine; U13C-DPPC, universally 13C-labeled dipalmitoyl PC.

768.5567 [M-H2O+NH4]+
PPM:10.8
Mus musculus Lung MALDI (DHB)
image5 - MTBLS2075
Resolution: 40μm, 163x183

Description

Supplementary Figure S8. MALDI-MSI data of mouse lung tissue administered with D9-choline and U 13C-DPPC–containing Poractant alfa surfactant (labels administered 18 h prior to sacrifice). Ion images of (a) m/z 796.6856 ([U13C-DPPC+Na]+), (b) m/z 756.5154 [PC32:0+Na]+ and (c) m/z 765.6079 ([D9-PC32:0+Na]+). (d) Overlay image of [U13C-DPPC+Na]+ (red) and [D9-PC32:0+Na]+ (green). Parts per million (ppm) mass errors are indicated in parentheses. All images were visualised using totalion-current normalisation and using hotspot removal (high quantile = 99%). DPPC = PC16:0/16:0.

769.559 [M+H]+
PPM:13
Mus musculus Lung MALDI (DHB)
image5 - MTBLS2075
Resolution: 40μm, 163x183

Description

Supplementary Figure S8. MALDI-MSI data of mouse lung tissue administered with D9-choline and U 13C-DPPC–containing Poractant alfa surfactant (labels administered 18 h prior to sacrifice). Ion images of (a) m/z 796.6856 ([U13C-DPPC+Na]+), (b) m/z 756.5154 [PC32:0+Na]+ and (c) m/z 765.6079 ([D9-PC32:0+Na]+). (d) Overlay image of [U13C-DPPC+Na]+ (red) and [D9-PC32:0+Na]+ (green). Parts per million (ppm) mass errors are indicated in parentheses. All images were visualised using totalion-current normalisation and using hotspot removal (high quantile = 99%). DPPC = PC16:0/16:0.

768.5565 [M-H2O+NH4]+
PPM:11
Mus musculus Lung MALDI (DHB)
image2 - MTBLS2075
Resolution: 40μm, 550x256

Description

Supplementary Figure S6. Ion distribution images for (a) [PC36:4+Na]+ (m/z 804.5514) and (b) [PC38:6+Na]+ (m/z 828.5515) obtained from mouse lung tissue collected 6 h after administration of D9- choline and U13C-DPPC–containing CHF5633. Parts-per-million (ppm) mass errors are indicated in parentheses. (c) Magnification of the boxed region in (a) with selected bronchiolar regions outlined in white boxes. (d) The corresponding H&E-stained tissue section with the same selected bronchiolar regions outlined in black boxes. These data demonstrate the co-localisation of the polyunsaturated lipids PC36:4 and PC38:6 with the bronchiolar regions of the lung. All MSI images were visualised using total ion current normalisation and hotspot removal (high quantile = 99%).

769.5582 [M+H]+
PPM:12
Mus musculus Lung MALDI (DHB)
image2 - MTBLS2075
Resolution: 40μm, 550x256

Description

Supplementary Figure S6. Ion distribution images for (a) [PC36:4+Na]+ (m/z 804.5514) and (b) [PC38:6+Na]+ (m/z 828.5515) obtained from mouse lung tissue collected 6 h after administration of D9- choline and U13C-DPPC–containing CHF5633. Parts-per-million (ppm) mass errors are indicated in parentheses. (c) Magnification of the boxed region in (a) with selected bronchiolar regions outlined in white boxes. (d) The corresponding H&E-stained tissue section with the same selected bronchiolar regions outlined in black boxes. These data demonstrate the co-localisation of the polyunsaturated lipids PC36:4 and PC38:6 with the bronchiolar regions of the lung. All MSI images were visualised using total ion current normalisation and hotspot removal (high quantile = 99%).

768.5586 [M-H2O+NH4]+
PPM:8.3
Macropus giganteus Brain MALDI (BPYN)
170321_kangaroobrain-dan3-pos_maxof50.0_med1 - 170321_kangaroobrain-dan3-pos_maxof50.0_med1
Resolution: 50μm, 81x50

Description

Sample information Organism: Macropus giganteus (kangaroo) Organism part: Brain Condition: Wildtype Sample growth conditions: Wild

769.5569 [M+H]+
PPM:10.3
Macropus giganteus Brain MALDI (BPYN)
170321_kangaroobrain-dan3-pos_maxof50.0_med1 - 170321_kangaroobrain-dan3-pos_maxof50.0_med1
Resolution: 50μm, 81x50

Description

Sample information Organism: Macropus giganteus (kangaroo) Organism part: Brain Condition: Wildtype Sample growth conditions: Wild

769.56 [M+H]+
PPM:14.3
Homo sapiens esophagus DESI ()
LNTO22_1_3 - MTBLS385
Resolution: 75μm, 121x68

Description

768.5414 [M]+
PPM:0.3
Homo sapiens esophagus DESI ()
LNTO22_1_4 - MTBLS385
Resolution: 17μm, 82x80

Description

769.5565 [M+H]+
PPM:9.7
Homo sapiens esophagus DESI ()
LNTO22_1_4 - MTBLS385
Resolution: 17μm, 82x80

Description

769.5587 [M+H]+
PPM:12.6
Homo sapiens esophagus DESI ()
LNTO29_16_2 - MTBLS385
Resolution: 17μm, 95x101

Description

769.5577 [M+H]+
PPM:11.3
Homo sapiens esophagus DESI ()
TO42T - MTBLS385
Resolution: 17μm, 69x81

Description

769.5605 [M+H]+
PPM:14.9
Homo sapiens esophagus DESI ()
LNTO22_1_9 - MTBLS385
Resolution: 75μm, 89x74

Description

769.5586 [M+H]+
PPM:12.5
Homo sapiens esophagus DESI ()
LNTO30_8M_1 - MTBLS385
Resolution: 17μm, 69x54

Description

768.5394 [M]+
PPM:2.3
Homo sapiens esophagus DESI ()
TO39T - MTBLS385
Resolution: 17μm, 69x81

Description

769.5578 [M+H]+
PPM:11.4
Homo sapiens esophagus DESI ()
TO39T - MTBLS385
Resolution: 17μm, 69x81

Description

768.5483 [M]+
PPM:9.3
Homo sapiens colorectal adenocarcinoma DESI ()
80TopL, 50TopR, 70BottomL, 60BottomR-profile - MTBLS415
Resolution: 17μm, 137x136

Description

The human colorectal adenocarcinoma sample was excised during a surgical operation performed at the Imperial College Healthcare NHS Trust. The sample and procedures were carried out in accordance with ethical approval (14/EE/0024).

769.5567 [M+H]+
PPM:10
Homo sapiens colorectal adenocarcinoma DESI ()
80TopL, 50TopR, 70BottomL, 60BottomR-profile - MTBLS415
Resolution: 17μm, 137x136

Description

The human colorectal adenocarcinoma sample was excised during a surgical operation performed at the Imperial College Healthcare NHS Trust. The sample and procedures were carried out in accordance with ethical approval (14/EE/0024).

768.5484 [M]+
PPM:9.4
Homo sapiens colorectal adenocarcinoma DESI ()
520TopL, 490TopR, 510BottomL, 500BottomR-profile - MTBLS415
Resolution: 17μm, 147x131

Description

The human colorectal adenocarcinoma sample was excised during a surgical operation performed at the Imperial College Healthcare NHS Trust. The sample and procedures were carried out in accordance with ethical approval (14/EE/0024).

769.5551 [M+H]+
PPM:7.9
Homo sapiens colorectal adenocarcinoma DESI ()
520TopL, 490TopR, 510BottomL, 500BottomR-profile - MTBLS415
Resolution: 17μm, 147x131

Description

The human colorectal adenocarcinoma sample was excised during a surgical operation performed at the Imperial College Healthcare NHS Trust. The sample and procedures were carried out in accordance with ethical approval (14/EE/0024).

769.5545 [M+H]+
PPM:7.1
Homo sapiens colorectal adenocarcinoma DESI ()
439TopL, 409TopR, 429BottomL, 419BottomR-profile - MTBLS415
Resolution: 17μm, 157x136

Description

The human colorectal adenocarcinoma sample was excised during a surgical operation performed at the Imperial College Healthcare NHS Trust. The sample and procedures were carried out in accordance with ethical approval (14/EE/0024).

769.5588 [M+H]+
PPM:12.7
Homo sapiens NA DESI ()
160TopL,130TopR,150BottomL,140BottomR-profile - MTBLS415
Resolution: 17μm, 142x136

Description

769.5585 [M+H]+
PPM:12.3
Homo sapiens esophagus DESI ()
LNTO29_16_3 - MTBLS385
Resolution: 17μm, 108x107

Description

768.5574 [M-H2O+NH4]+
PPM:9.9
Homo sapiens esophagus DESI ()
LNTO26_7_1 - MTBLS385
Resolution: 17μm, 75x74

Description

769.5599 [M+H]+
PPM:14.2
Homo sapiens esophagus DESI ()
LNTO26_7_1 - MTBLS385
Resolution: 17μm, 75x74

Description

769.5598 [M+H]+
PPM:14
Homo sapiens esophagus DESI ()
LNTO26_7_3 - MTBLS385
Resolution: 75μm, 82x88

Description

768.5419 [M]+
PPM:0.9
Homo sapiens esophagus DESI ()
TO40T - MTBLS385
Resolution: 17μm, 82x74

Description

769.5563 [M+H]+
PPM:9.5
Homo sapiens esophagus DESI ()
TO40T - MTBLS385
Resolution: 17μm, 82x74

Description

768.5456 [M]+
PPM:5.8
Homo sapiens esophagus DESI ()
TO31T - MTBLS385
Resolution: 75μm, 56x54

Description

769.5584 [M+H]+
PPM:12.2
Homo sapiens esophagus DESI ()
TO31T - MTBLS385
Resolution: 75μm, 56x54

Description

769.5585 [M+H]+
PPM:12.3
Homo sapiens esophagus DESI ()
TO41T - MTBLS385
Resolution: 75μm, 69x43

Description

769.5588 [M+H]+
PPM:12.7
Homo sapiens esophagus DESI ()
LNTO30_8M_2 - MTBLS385
Resolution: 75μm, 108x68

Description

768.5449 [M]+
PPM:4.8
Homo sapiens esophagus DESI ()
LNTO30_8M_3 - MTBLS385
Resolution: 75μm, 69x54

Description

769.5587 [M+H]+
PPM:12.6
Homo sapiens esophagus DESI ()
LNTO30_8M_3 - MTBLS385
Resolution: 75μm, 69x54

Description

769.5594 [M+H]+
PPM:13.5
Homo sapiens esophagus DESI ()
LNTO30_8M_4 - MTBLS385
Resolution: 75μm, 62x48

Description

768.5449 [M]+
PPM:4.8
Homo sapiens esophagus DESI ()
LNTO30_8M_5 - MTBLS385
Resolution: 75μm, 56x54

Description

769.5589 [M+H]+
PPM:12.9
Homo sapiens esophagus DESI ()
LNTO30_8M_5 - MTBLS385
Resolution: 75μm, 56x54

Description

769.5589 [M+H]+
PPM:12.9
Homo sapiens esophagus DESI ()
LNTO30_17_2 - MTBLS385
Resolution: 75μm, 82x54

Description

769.5603 [M+H]+
PPM:14.7
Homo sapiens esophagus DESI ()
LNTO22_1_5 - MTBLS385
Resolution: 75μm, 135x94

Description

769.56 [M+H]+
PPM:14.3
Homo sapiens esophagus DESI ()
LNTO22_1_7 - MTBLS385
Resolution: 75μm, 69x54

Description

733.5244 [M+H-2H2O]+
PPM:4.7
Homo sapiens esophagus DESI ()
LNTO22_1_8 - MTBLS385
Resolution: 75μm, 69x61

Description

769.5597 [M+H]+
PPM:13.9
Homo sapiens esophagus DESI ()
LNTO22_1_8 - MTBLS385
Resolution: 75μm, 69x61

Description

769.5596 [M+H]+
PPM:13.8
Homo sapiens esophagus DESI ()
LNTO22_2_1 - MTBLS385
Resolution: 75μm, 89x88

Description

769.5602 [M+H]+
PPM:14.6
Homo sapiens esophagus DESI ()
LNTO22_2_2 - MTBLS385
Resolution: 75μm, 135x94

Description

768.5573 [M-H2O+NH4]+
PPM:10
Homo sapiens esophagus DESI ()
LNTO26_16_1 - MTBLS385
Resolution: 75μm, 95x88

Description

769.56 [M+H]+
PPM:14.3
Homo sapiens esophagus DESI ()
LNTO26_16_1 - MTBLS385
Resolution: 75μm, 95x88

Description

768.5446 [M]+
PPM:4.5
Homo sapiens esophagus DESI ()
LNTO29_18_2 - MTBLS385
Resolution: 75μm, 62x68

Description

769.5585 [M+H]+
PPM:12.3
Homo sapiens esophagus DESI ()
LNTO29_18_2 - MTBLS385
Resolution: 75μm, 62x68

Description

769.5589 [M+H]+
PPM:12.9
Homo sapiens esophagus DESI ()
LNTO30_7_1 - MTBLS385
Resolution: 75μm, 69x68

Description

769.5588 [M+H]+
PPM:12.7
Homo sapiens esophagus DESI ()
LNTO30_7_2 - MTBLS385
Resolution: 75μm, 82x68

Description

786.5892 [M+NH4]+
PPM:17.4
Mus musculus brain MALDI (DHB)
Brain01_Bregma1-42_02_centroid - MTBLS313
Resolution: 17μm, 434x258

Description

769.5583 [M+H]+
PPM:12.1
Homo sapiens colorectal adenocarcinoma DESI ()
240TopL, 210TopR, 230BottomL, 220BottomR-centroid - MTBLS176
Resolution: 50μm, 142x141

Description

769.5589 [M+H]+
PPM:12.9
Homo sapiens colorectal adenocarcinoma DESI ()
200TopL, 170TopR, 190BottomL, 180BottomR-centroid - MTBLS176
Resolution: 50μm, 132x126

Description

769.5581 [M+H]+
PPM:11.8
Homo sapiens colorectal adenocarcinoma DESI ()
160TopL,130TopR,150BottomL,140BottomR-centroid - MTBLS176
Resolution: 50μm, 142x136

Description

769.5587 [M+H]+
PPM:12.6
Homo sapiens colorectal adenocarcinoma DESI ()
120TopL, 90TopR, 110BottomL, 100BottomR-centroid - MTBLS176
Resolution: 50μm, 132x136

Description

769.555 [M+H]+
PPM:7.8
Drosophila melanogaster brain MALDI (DHB)
Drosophila18 - 2019-10-16_14h26m34s
Resolution: 5μm, 686x685

Description

Sample information Organism: Drosophila melanogaster Organism part: Brain Condition: Healthy Sample preparation Sample stabilisation: Frozen Tissue modification: Frozen MALDI matrix: 2,5-dihydroxybenzoic acid (DHB) MALDI matrix application: TM sprayer Solvent: Aceton/water MS analysis Polarity: Positive Ionisation source: Prototype Analyzer: Orbitrap Pixel size: 5μm × 5μm Annotation settings m/z tolerance (ppm): 3 Analysis version: Original MSM Pixel count: 469910 Imzml file size: 696.23 MB Ibd file size: 814.11 MB


SM(d17:1/20:4(6Z,8E,10E,14Z)-2OH(5S,12R)) is a type of oxidized sphingolipid found in animal cell membranes. It usually consists of phosphorylcholine and ceramide. SM(d17:1/20:4(6Z,8E,10E,14Z)-2OH(5S,12R)) consists of a sphingosine backbone and a Leukotriene B4 chain. In humans, sphingomyelin is the only membrane phospholipid not derived from glycerol. Like all sphingolipids, SM has a ceramide core (sphingosine bonded to a fatty acid via an amide linkage). In addition, it contains one polar head group, which is either phosphocholine or phosphoethanolamine. The plasma membrane of cells is highly enriched in sphingomyelin and is considered largely to be found in the exoplasmic leaflet of the cell membrane. However, there is some evidence that there may also be a sphingomyelin pool in the inner leaflet of the membrane. Moreover, neutral sphingomyelinase-2, an enzyme that breaks down sphingomyelin into ceramide, has been found to localize exclusively to the inner leaflet further suggesting that there may be sphingomyelin present there. Sphingomyelin can accumulate in a rare hereditary disease called Niemann-Pick Disease, types A and B. Niemann-Pick disease is a genetically-inherited disease caused by a deficiency in the enzyme sphingomyelinase, which causes the accumulation of sphingomyelin in spleen, liver, lungs, bone marrow, and the brain, causing irreversible neurological damage. SMs play a role in signal transduction. Sphingomyelins are synthesized by the transfer of phosphorylcholine from phosphatidylcholine to a ceramide in a reaction catalyzed by sphingomyelin synthase.