Fluorescent Lipids

Introduction

Fluorescent lipids are the lipids that attach fluorophores to lipid molecules. Lipids are amphiphilic in nature and consist of a hydrophobic acyl chain and a hydrophilic head group region. Accordingly, there are in principle two regions within the molecule to which fluorophores can be covalently coupled. Fluorescent lipids are the preferred tool for the investigation of biological functions involving the membrane biophysics, lipid biochemistry and cell biology due to their particular photophysical properties ^[1].

Fig.1 Schematic representation of fluorescent lipid probes highlighting the location of the fluorophore at the (a) headgroup and (b) acyl chain

Classification

Fluorescent lipids can be divided into the following categories according to fluorophores.

• Nitrobenzoxadiazole (NBD) labeled lipids. NBD is the most popular fluorophore used in fluorescent lipids. Irrespective of attachment to the lipid head group or hydrocarbon chains, the NBD fluorophore generally adopts a transverse bilayer location near the host lipid carbonyl/glycerol moieties. NBD labeled lipids are popular fluorescent probes of membrane structure and dynamics, and have been widely used in both model systems and living cells ^[2].

Fig.2 Structure of NBD labeled lipids

• Pyrene labeled lipids. Pyrene is one of the most frequently used lipid-linked fluorophores. It has the features of long excited state lifetime and concentration-dependent formation of excimers, and does not significantly distort the conformation of the labeled lipid molecule due to its hydrophobic. These characteristics make pyrene labeled lipids well-suited for studies on a variety of membranes biophysical phenomena, protein interaction and cell biology like lipid trafficking and metabolism ^[3].

Fig.3 Structures of pyrene labeled lipids

• BODIPY labeled lipids. BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) have been found a wide range of applications in fluorescent lipids because of its overall excellent spectral properties, which include high photostability, high molar absorptivity, high quantum yields, and strong, narrow-wavelength emission maxima in the visible region. BODIPY labeled lipids includes labeled fatty acids and complex lipid, which have been applied in numerous biological studies such as cell biology and biophysics ^[4].
• Cyanine labeled lipids. Among a wide variety of fluorophores used in fluorescent lipids, the near-infrared (NIR) cyanine also has received much considerable attention due to their advantageous photophysical properties, namely absorption and fluorescence spectrum in the NIR region (670-1100 nm). Cyanine has a wide class, among them, cyanine 3, cyanine 5, cyanine 7 are frequently used in construction of fluorescent lipids, the resulted lipids are the excellent probe for bioimaging in biological study.

Applications

Basically, the applications of fluorescent lipid can be divided into two main classes according to study object. One of them includes studies where the fluorescent lipid is used as a probe providing information on particular properties of a system, such as "membrane fluidity". In this case the labeled lipid is used as a "system probe". The other class includes investigations aimed at understanding the behavior of a single lipid molecule, such as its conformation or transbilayer movement, for example ^[3].

In addition, the applications of fluorescent lipid can be divided into also two main categories according to research field, which is the most common way of classification. The details are shown in below.

• Application in membrane biophysics. Fluorescent lipids can be used in study of the lateral diffusion and fluidity, lateral arrangement of lipid bilayers, lipid-protein interactions, lipid-lipid interactions, inter- and transbilayer translocation of lipids, membrane fusion, lipid conformation, polarity of membranes and others.
• Application in cell biology and biochemistry. In this case, the fluorescent lipids can be used in study of lipid trafficking, lipid metabolism, assay of lipolytic enzymes, microscopic mapping of membrane properties, cell biology and many others.

Alfa Chemistry can offer various fluorescent lipids. You can click on our product list for a detailed view. If you do not find the product you want, we also provide you with custom synthesis service. Please contact us, if you are in need of assistance.

References

1. Varandas P. A. M. M., et al. Emergent glycerophospholipid fluorescent probes: synthesis and applications[J]. Bioconjugate Chemistry, 2019, 31(3): 417-435.
2. Filipe H. A. L., et al. Orientation of nitro-group governs the fluorescence lifetime of nitrobenzoxadiazole (NBD)-labeled lipids in lipid bilayers[J]. Physical Chemistry Chemical Physics, 2019, 21(4): 1682-1688.
3. Somerharju P. Pyrene-labeled lipids as tools in membrane biophysics and cell biology[J]. Chemistry and Physics of Lipids, 2002, 116(1-2): 57-74.
4. Boldyrev I. A., et al. New BODIPY lipid probes for fluorescence studies of membranes[J]. Journal of Lipid Research, 2007, 48(7): 1518-1532.