The plasma membrane is a complex system, consisting of two layers of lipids and proteins compartmentalized into small structures called nanodomains. Despite the asymmetric composition of both leaflets, coupling between the layers is surprisingly strong. This can be evidenced, for example, by recent experimental studies performed on phospholipid giant unilamellar vesicles showing that nanodomains formed in the outer layer are perfectly registered with those in the inner leaflet. Similarly, microscopic phase separation in one leaflet can induce phase separation in the opposing leaflet that would otherwise be homogeneous. In this review, we summarize the current theoretical and experimental knowledge that led to the current view that domains are - irrespective of their size - commonly registered across the bilayer. Mechanisms inducing registration of nanodomains suggested by theory and calculations are discussed. Furthermore, domain coupling is evidenced by experimental studies based on the sparse number of methods that can resolve registered from independent nanodomains. Finally, implications that those findings using model membrane studies might have for cellular membranes are discussed.

• Klíčová slova
• biomembranes, domain registration, interleaflet coupling, membrane asymmetry, nanodomains, phase separation, plasma membranes,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

Understanding interactions of calcium with lipid membranes at the molecular level is of great importance in light of their involvement in calcium signaling, association of proteins with cellular membranes, and membrane fusion. We quantify these interactions in detail by employing a combination of spectroscopic methods with atomistic molecular dynamics simulations. Namely, time-resolved fluorescent spectroscopy of lipid vesicles and vibrational sum frequency spectroscopy of lipid monolayers are used to characterize local binding sites of calcium in zwitterionic and anionic model lipid assemblies, while dynamic light scattering and zeta potential measurements are employed for macroscopic characterization of lipid vesicles in calcium-containing environments. To gain additional atomic-level information, the experiments are complemented by molecular simulations that utilize an accurate force field for calcium ions with scaled charges effectively accounting for electronic polarization effects. We demonstrate that lipid membranes have substantial calcium-binding capacity, with several types of binding sites present. Significantly, the binding mode depends on calcium concentration with important implications for calcium buffering, synaptic plasticity, and protein-membrane association.

• MeSH
• buněčná membrána metabolismus   MeSH
• fosfolipidy chemie   metabolismus   MeSH
• lipidové dvojvrstvy chemie   metabolismus   MeSH
• liposomy chemie   metabolismus   MeSH
• molekulární modely MeSH
• simulace molekulární dynamiky MeSH
• vápník metabolismus   MeSH
• vápníková signalizace MeSH
• vazebná místa MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• fosfolipidy MeSH
• lipidové dvojvrstvy MeSH
• liposomy MeSH
• vápník MeSH

The effect of sodium, potassium, and lithium on δ-opioid receptor ligand binding parameters and coupling with the cognate G proteins was compared in model HEK293 cell line stably expressing PTX-insensitive δ-OR-Gi1α (Cys(351)-Ile(351)) fusion protein. Agonist [(3)H]DADLE binding was decreased in the order Na(+) ≫ Li(+) > K(+) > (+)NMDG. When plotted as a function of increasing NaCl concentrations, the binding was best-fitted with a two-phase exponential decay considering two Na(+)-responsive sites (r (2) = 0.99). High-affinity Na(+)-sites were characterized by Kd = 7.9 mM and represented 25 % of the basal level determined in the absence of ions. The remaining 75 % represented the low-affinity sites (Kd = 463 mM). Inhibition of [(3)H]DADLE binding by lithium, potassium, and (+)-NMDG proceeded in low-affinity manner only. Surprisingly, the affinity/potency of DADLE-stimulated [(35)S]GTPγS binding was increased in a reverse order: Na(+) < K(+) < Li(+). This result was demonstrated in PTX-treated as well as PTX-untreated cells. Therefore, it is not restricted to Gi1α(Cys(351)-Ile(351)) within the δ-OR-Gi1α fusion protein, but is also valid for stimulation of endogenous G proteins of Gi/Go family in HEK293 cells. Biophysical studies of interaction of ions with polar head-group region of lipids using Laurdan generalized polarization indicated the low-affinity type of interaction only proceeding in the order: Cs(+) < K(+) < Na(+) < Li(+). The results are discussed in terms of interaction of Na(+), K(+) and Li(+) with the high- and low-affinity sites located in water-accessible part of δ-OR binding pocket. We also consider the role of negatively charged Cl(-), Br(-), and I(-) counter anions in inhibition of both [(3)H]DADLE and [(35)S]GTPγS binding.

• MeSH
• buněčná membrána metabolismus   MeSH
• guanosin 5'-O-(3-thiotrifosfát) metabolismus   MeSH
• HEK293 buňky MeSH
• leucin-2-alanin-enkefalin metabolismus   MeSH
• lidé MeSH
• lipidové dvojvrstvy metabolismus   MeSH
• lithium farmakologie   MeSH
• proteiny vázající GTP - alfa-podjednotky Gi-Go metabolismus   MeSH
• receptory opiátové delta metabolismus   MeSH
• rekombinantní proteiny metabolismus   MeSH
• sodík metabolismus   MeSH
• vazebná místa MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• guanosin 5'-O-(3-thiotrifosfát) MeSH
• leucin-2-alanin-enkefalin MeSH
• lipidové dvojvrstvy MeSH
• lithium MeSH
• proteiny vázající GTP - alfa-podjednotky Gi-Go MeSH
• receptory opiátové delta MeSH
• rekombinantní proteiny MeSH
• sodík MeSH

Fluorescence correlation spectroscopy (FCS) is a single molecule technique used mainly for determination of mobility and local concentration of molecules. This review describes the specific problems of FCS in planar systems and reviews the state of the art experimental approaches such as 2-focus, Z-scan or scanning FCS, which overcome most of the artefacts and limitations of standard FCS. We focus on diffusion measurements of lipids and proteins in planar lipid membranes and review the contributions of FCS to elucidating membrane dynamics and the factors influencing it, such as membrane composition, ionic strength, presence of membrane proteins or frictional coupling with solid support.

• Klíčová slova
• biomembranes, confocal microscopy, fluorescence fluctuation spectroscopy, giant unilamellar vesicles, lateral diffusion, supported lipid bilayers,
• MeSH
• difuze MeSH
• fluorescenční spektrometrie * MeSH
• konfokální mikroskopie MeSH
• lipidové dvojvrstvy chemie   MeSH
• membránové lipidy chemie   MeSH
• unilamelární lipozómy chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• lipidové dvojvrstvy MeSH
• membránové lipidy MeSH
• unilamelární lipozómy MeSH

We present molecular dynamics simulations of a multicomponent, asymmetric bilayer in mixed aqueous solutions of sodium and potassium chloride. Because of the geometry of the system, there are two aqueous solution regions in our simulations: one mimics the intracellular region, and one mimics the extracellular region. Ion-specific effects are evident at the membrane/aqueous solution interface. Namely, at equal concentrations of sodium and potassium, sodium ions are more strongly adsorbed to carbonyl groups of the lipid headgroups. A significant concentration excess of potassium is needed for this ion to overwhelm the sodium abundance at the membrane. Ion-membrane interactions also lead to concentration-dependent and cation-specific behavior of the electrostatic potential in the intracellular region because of the negative charge on the inner leaflet. In addition, water permeation across the membrane was observed on a timescale of approximately 100 ns. This study represents a step toward the modeling of realistic biological membranes at physiological conditions in intracellular and extracellular environments.

• MeSH
• buněčná membrána chemie   MeSH
• časové faktory MeSH
• chemické modely * MeSH
• chlorid draselný chemie   MeSH
• chlorid sodný chemie   MeSH
• draslík chemie   MeSH
• fosfatidylcholiny chemie   MeSH
• fosfatidylethanolaminy chemie   MeSH
• fosfatidylseriny chemie   MeSH
• membrány umělé MeSH
• permeabilita buněčné membrány MeSH
• počítačová simulace MeSH
• sfingomyeliny chemie   MeSH
• sodík chemie   MeSH
• statická elektřina MeSH
• voda chemie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• 1-palmitoyl-2-oleoylglycero-3-phosphoserine MeSH Prohlížeč
• 1-palmitoyl-2-oleoylphosphatidylcholine MeSH Prohlížeč
• 1-palmitoyl-2-oleoylphosphatidylethanolamine MeSH Prohlížeč
• chlorid draselný MeSH
• chlorid sodný MeSH
• draslík MeSH
• fosfatidylcholiny MeSH
• fosfatidylethanolaminy MeSH
• fosfatidylseriny MeSH
• membrány umělé MeSH
• palmitoylsphingomyelin MeSH Prohlížeč
• sfingomyeliny MeSH
• sodík MeSH
• voda MeSH