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Subramaniam R, Lynch S, Cen Y, Balaz S. Polarity of Hydrated Phosphatidylcholine Headgroups. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:8460-8471. [PMID: 31244216 PMCID: PMC6853183 DOI: 10.1021/acs.langmuir.8b03992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The headgroup (H) stratum (sometimes called the polar region) of membrane bilayers is a relevant yet poorly understood solvation phase for small molecules and macromolecules interacting with the membranes. Solvation of compounds in bilayer strata is characterized experimentally by wide- and small-angle X-ray scattering, neutron diffraction, and various NMR techniques. The quantification is tedious and only available for a limited set of small molecules. Our recently published model of liposome partitioning of small molecules shows that solvation of compounds in the H-stratum of fluid phosphatidylcholine (PC) bilayers correlates well with their solvation in hydrated diacetyl phosphatidylcholine (DAcPC), and solvation in the core (C) depends in a similar way on that in n-hexadecane. These two correlations became a basis for a model describing the location of compounds in the H- and C-strata and at the connecting interface as a nonlinear function of the fragment solvation characteristics of the compounds. In this study, refractivity of hydrated DAcPC phases with varying water contents was measured and polarity was determined using the steady-state fluorescence of indole and Nile Red. The results were compared with the published data obtained by other techniques for PC bilayers in liposomes or on solid supports. The demonstrated qualitative agreement, as well as the polarity and refractivity dependencies on the DAcPC concentration, supports the suitability of hydrated DAcPC as the H-stratum surrogate. Interestingly, depending on hydrations typical for the H-strata of fluid PC bilayers, the dielectric constant could decrease significantly from 31.0 to 7.3 for 16 and 8 water molecules per headgroup, respectively. Although additional experiments are needed for confirmation, this observation could help set proper dielectric constant magnitudes in continuum-based computational models of accumulation and crossing of the PC bilayers with varying hydration levels thanks to the temperature or the structure of fatty acid chains.
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Affiliation(s)
| | | | | | - Stefan Balaz
- Corresponding author: Stefan Balaz, Albany College of Pharmacy and Health Sciences, Vermont Campus, Department of Pharmaceutical Sciences, 261 Mountain View Road, Colchester, VT 05446, United States, phone 802-735-2615,
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Waybright J, Huang W, Proctor A, Wang X, Allbritton NL, Zhang Q. Required hydrophobicity of fluorescent reporters for phosphatidylinositol family of lipid enzymes. Anal Bioanal Chem 2017; 409:6781-6789. [PMID: 28932942 DOI: 10.1007/s00216-017-0633-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 08/31/2017] [Accepted: 09/11/2017] [Indexed: 12/13/2022]
Abstract
The phosphatidylinositol (PtdIns) family of lipids plays important roles in cell differentiation, proliferation, and migration. Abnormal expression, mutation, or regulation of their metabolic enzymes has been associated with various human diseases such as cancer, diabetes, and bipolar disorder. Recently, fluorescent derivatives have increasingly been used as chemical probes to monitor either lipid localization or enzymatic activity. However, the requirements of a good probe have not been well defined, particularly modifications on the diacylglycerol side chain partly due to challenges in generating PtdIns lipids. We have synthesized a series of fluorescent PtdIns(4,5)P2 (PIP2) and PtdIns (PI) derivatives with various lengths of side chains and tested their capacity as substrates for PI3KIα and PI4KIIα, respectively. Both capillary electrophoresis and thin-layer chromatography were used to analyze enzymatic reactions. For both enzymes, the fluorescent probe with a longer side chain functions as a better substrate than that with a shorter chain and works well in the presence of the endogenous lipid, highlighting the importance of hydrophobicity of side chains in fluorescent phosphoinositide reporters. This comparison is consistent with their interactions with lipid vesicles, suggesting that the binding of a fluorescent lipid with liposome serves as a standard for assessing its utility as a chemical probe for the corresponding endogenous lipid. These findings are likely applicable to other lipid enzymes where the catalysis takes place at the lipid-water interface.
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Affiliation(s)
- Jarod Waybright
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, 301 Pharmacy Lane, Chapel Hill, NC, 27599, USA
| | - Weigang Huang
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, 301 Pharmacy Lane, Chapel Hill, NC, 27599, USA
| | - Angela Proctor
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Xiaoyang Wang
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, 301 Pharmacy Lane, Chapel Hill, NC, 27599, USA
| | - Nancy L Allbritton
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA.,Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Campus Box 3290, Chapel Hill, NC, 27599, USA.,North Carolina State University, Raleigh, NC, 27695, USA
| | - Qisheng Zhang
- Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, 301 Pharmacy Lane, Chapel Hill, NC, 27599, USA.
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Subramaniam R, Jagadeesan R, Mathew I, Cen Y, Balaz S. Scalable Synthesis and Purification of Acetylated Phosphatidyl Choline Headgroup. Org Process Res Dev 2017; 21:177-181. [PMID: 30792570 DOI: 10.1021/acs.oprd.6b00261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The acetylated headgroup of the most abundant mammalian phospholipid, 1,2-diacetyl-3-sn-phosphatidyl choline (DAcPC), has several important applications in research. For instance, it can be dissolved in the same amount of water as in the fluid PC bilayer, to create a surrogate of a PC headgroup stratum, for studying solvation of small molecules and the influence of their structure on the process. In contrast to PC derivatives with longer acyl chains, DAcPC does not self-aggregate, rendering the aqueous solution homogeneous and suitable for simplified analyses of interactions of molecules with the headgroups. Several studies have been published where DAcPC was used in a crudely purified form. Here we describe a one-step preparation of DAcPC from commercially available bulk chemicals and purification of the product by crystallization and washing. The process gives a good yield and is easily scalable. The availability of enantiopure, crystalline DAcPC could open the door to more extensive biochemical, pharmacological, and nutritional studies of this interesting chemical.
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Affiliation(s)
- Rajesh Subramaniam
- Department of Pharmaceutical Sciences, Vermont Campus, Albany College of Pharmacy and Health Sciences, 261 Mountain View Drive, Colchester, Vermont 05446, Unites States
| | - Ramesh Jagadeesan
- Pharmaceutical Development Unit, Kemwell Biopharma Pvt Ltd, 34 Tumkur Road, T-Begur, Nelamangala, Bangalore Rural-562123, India
| | - Iswarya Mathew
- Department of Pharmaceutical Sciences, Vermont Campus, Albany College of Pharmacy and Health Sciences, 261 Mountain View Drive, Colchester, Vermont 05446, Unites States
| | - Yana Cen
- Department of Pharmaceutical Sciences, Vermont Campus, Albany College of Pharmacy and Health Sciences, 261 Mountain View Drive, Colchester, Vermont 05446, Unites States
| | - Stefan Balaz
- Department of Pharmaceutical Sciences, Vermont Campus, Albany College of Pharmacy and Health Sciences, 261 Mountain View Drive, Colchester, Vermont 05446, Unites States
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Goñi FM, Montes LR, Alonso A. Phospholipases C and sphingomyelinases: Lipids as substrates and modulators of enzyme activity. Prog Lipid Res 2012; 51:238-66. [DOI: 10.1016/j.plipres.2012.03.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 03/23/2012] [Accepted: 03/26/2012] [Indexed: 11/30/2022]
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Urbina P, Collado MI, Alonso A, Goñi FM, Flores-Díaz M, Alape-Girón A, Ruysschaert JM, Lensink MF. Unexpected wide substrate specificity of C. perfringens α-toxin phospholipase C. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:2618-27. [DOI: 10.1016/j.bbamem.2011.06.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/09/2011] [Accepted: 06/13/2011] [Indexed: 02/05/2023]
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Foglia F, Lawrence MJ, Lorenz CD, McLain SE. On the hydration of the phosphocholine headgroup in aqueous solution. J Chem Phys 2011; 133:145103. [PMID: 20950050 DOI: 10.1063/1.3488998] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The hydration of the phosphocholine headgroup in 1,2-dipropionyl-sn-glycero-3-phosphocholine (C(3)-PC) in solution has been determined by using neutron diffraction enhanced with isotopic substitution in combination with computer simulation techniques. The atomic scale hydration structure around this head group shows that both the -N(CH(3))(3) and -CH(2) portions of the choline headgroup are strongly associated with water, through a unique hydrogen bonding regime, where specifically a hydrogen bond from the C-H group to water and a strong association between the water oxygen and N(+) atom in solution have both been observed. In addition, both PO(4) oxygens (P=O) and C=O oxygens are oversaturated when compared to bulk water in that the average number of hydrogen bonds from water to both X=O oxygens is about 2.5 for each group. That water binds strongly to the glycerol groups and is suggestive that water may bind to these groups when phosophotidylcholine is embedded in a membrane bilayer.
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Affiliation(s)
- Fabrizia Foglia
- Department of Pharmaceutical Sciences, King's College London, London SE1 9NH, United Kingdom
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Discrimination of Chain Positions in Mixed Short/Long-Chain Glycerophosphocholines by NMR Chemical Shift Variations. J AM OIL CHEM SOC 2008. [DOI: 10.1007/s11746-008-1280-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Benfield AP, Goodey NM, Phillips LT, Martin SF. Structural studies examining the substrate specificity profiles of PC-PLC(Bc) protein variants. Arch Biochem Biophys 2007; 460:41-7. [PMID: 17324372 PMCID: PMC1905842 DOI: 10.1016/j.abb.2007.01.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Revised: 01/18/2007] [Accepted: 01/23/2007] [Indexed: 10/23/2022]
Abstract
The phosphatidylcholine preferring phospholipase C from Bacillus cereus (PC-PLC(Bc)) catalyzes the hydrolysis of phospholipids in the following order of preference: phosphatidylcholine (PC)>phosphatidylethanolamine (PE)>phosphatidylserine (PS). In previous work, mutagenic, kinetic, and crystallographic experiments suggested that varying the amino acids at the 4th, 56th, and 66th positions had a significant influence upon the substrate specificity profile of PC-PLC(Bc). Here, we report the crystal structures of the native form of several PC-PLC(Bc) variants that exhibited altered substrate specificities for PC, PE, and PS at maximum resolutions of 1.90-2.05 Angstrom. Comparing the structures of these variants to the structure of the wild-type enzyme reveals only minor differences with respect to the number and location of active site water molecules and the side chain conformations of residues at the 4th and 56th positions. These results suggest that subtle changes in steric and electronic properties in the substrate binding site of PC-PLC(Bc) are responsible for the significant changes in substrate selectivity.
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Affiliation(s)
- Aaron P Benfield
- Department of Chemistry and Biochemistry, The Institute of Cellular and Molecular Biology, The University of Texas, 1 University Station - A5300, Austin, TX 78712, USA
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González-Roura A, Casas J, Llebaria A. Synthesis and phospholipase C inhibitory activity of D609 diastereomers. Lipids 2002; 37:401-6. [PMID: 12030321 DOI: 10.1007/s1145-002-0908-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The potassium xanthate D609 is widely accepted as a selective inhibitor of PC-specific phospholipase C (PC-PLC). The tricyclo[5.2.1.(02,6)]decane skeleton present in D609 can lead to four diastereomeric pairs, but the diastereoselectivity of PC-PLC inhibition has never been reported. In this article, the synthesis of racemic D609 diastereomers and that of other xanthates, as well as their inhibitory effect on PC-PLC is reported. All xanthates obtained were competitive inhibitors of PC-PLC from Bacillus cereus (PLCBc). No significant differences were found in the activity of D609 diastereomers (Ki 13-17 microM), suggesting the absence of a diastereochemical control of the enzyme by xanthate inhibitors. This result was confirmed after obtaining other potassium xanthates differing from D609 in the aliphatic chain. Among them, the potassium O-n-decenylxanthate was the most active inhibitor of PLCBc (Ki 10 microM). These data indicate that the essential structural requirements for PLCBc in vitro inhibition by xanthates are the presence of a Zn-chelating dithiocarbonate head and a sufficiently hydrophobic aliphatic moiety.
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Abstract
To characterize the specificity of zinc binding to phospholipid membranes in terms of headgroup structure, hydration and phase behavior we studied the zwitterionic lipid 1-palmitoyl-2-oleoyl-phosphatidylcholine as a function of hydration at 30 degreesC in the presence and absence of ZnCl2. Zinc forms a 2:1-1:1 complex with the lipid, and in particular with the negatively charged phosphate groups. Zn2(+)-bridges between neighboring lipid molecules stabilize the gel phase of the lipid relative to the liquid-crystalline state. Upon Zn2+ binding the C-O-P-O-C- backbone of the lipid headgroup changes from a gauche/gauche into the trans/trans conformation and it loses roughly 50% of the hydration shell. The ability of the Zn2(+)-bound phosphate groups to take up water is distinctly reduced, meaning that the headgroups have become less hydrophilic. The energetic cost (on the scale of Gibbs free energy) for completely dehydrating the lipid headgroups is decreased by approximately 10 kJ/mole in the presence of Zn2+. The interaction of phospholipid headgroups with Zn2+ is conveniently described by a hydrated zinc-phosphate complex the key energy contribution of which is more covalent than electrostatic in nature. Dehydration of phospholipid headgroups due to complexation with zinc cations is suggested to increase fusogenic potency of lipid membranes. Zinc appears to be one of the most potent divalent cation in inducing membrane fusion.
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Affiliation(s)
- H Binder
- University of Leipzig, Institute of Medical Physics and Biophysics, Germany.
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Abstract
The physico-chemical properties of short-chain phosphatidylcholine are reviewed to the extent that its biological activity as a mild detergent can be rationalized. Long-chain diacylphosphatidylcholines are typical membrane phospholipids that form preferentially smectic lamellar phases (bilayers) when dispersed in water. In contrast, the preferred phase of the short-chain analogues dispersed in excess water is the micellar phase. The preferred conformation and the dynamics of short-chain phosphatidylcholines in the monomeric and micellar state present in H(2)O are discussed. The motionally averaged conformation of short-chain phosphatidylcholines is then compared to the single-crystal structures of membrane lipids. The main conclusion emerging is that in terms of preferred conformation and motional averaging short-chain phosphatidylcholines closely resemble their long-chain analogues. The dispersing power of short-chain phospholipids is emphasized in the second part of the review. Evidence is presented to show that this class of compounds is superior to most other detergents used in the solubilization of membrane proteins and the reconstitution of the solubilized proteins to artificial membrane systems (proteoliposomes). The prominent feature of the solubilization/reconstitution of integral membrane proteins by short-chain PC is the retention of the native protein structure and hence the protein function. Due to their special detergent-like properties, short-chain PC lend themselves very well not only to membrane solubilization but also to the purification of integral membrane proteins. The retention of the native protein structure in the solubilized state, i.e. in mixed micelles consisting of the integral membrane protein, intrinsic membrane lipids and short-chain PC, is rationalized. It is hypothesized that short-chain PC interacts primarily with the lipid bilayer of a membrane and very little if at all with the membrane proteins. In this way, the membrane protein remains associated with its preferred intrinsic membrane lipids and retains its native structure and its function.
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Affiliation(s)
- H Hauser
- Institute of Biochemistry, Swiss Federal Institute of Technology, ETH Centre, Universitätsstrasse 16, CH-8092, Zurich, Switzerland.
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Phosphatidylcholine-Preferring Phospholipase C from B. cereus. Function, Structure, and Mechanism. Top Curr Chem (Cham) 2000. [DOI: 10.1007/3-540-45035-1_5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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