Interactions of a Photochromic Spiropyran with Liposome Model Membranes

Abstract

The interactions between anionic or zwitterionic liposomes and a water-soluble, DNA-binding photochromic spiropyran are studied using UV/vis absorption and linear dichroism (LD) spectroscopy. The spectral characteristics as well as the kinetics of the thermal isomerization process in the absence and presence of the two different liposome types provide information about the environment and whether or not the spiropyran resides in the liposome membrane. By measuring LD on liposomes deformed and aligned by shear flow, further insight is obtained about interaction and binding geometry of the spiropyran at the lipid membranes. We show that the membrane interactions differ between the two types of liposomes used as well as the isomeric forms of the spiropyran photoswitch.

Photoswitchable phospholipid FRET acceptor: Detergent free intermembrane transfer assay of fluorescent lipid analogs

“…3, dotted line). After UV (365 nm) irradiation, N -nitroBIPS-DPPG showed MC absorption 17 with an absorption maximum at 543 nm (Fig. 3, solid line).…”

“…This confirms that conjugation of N -nitroBIPS-ethanol to phospholipids does not impede its photoswitching between the SP and MC species. Additionally, MC is known to exhibit solvatochromism, as reduced solvent polarity and H-bonding capability is associated with a red shift of its absorption maximum from 510 nm to 540 nm and 570 nm in water, ethanol and acetone, respectively 17 . The observed red shift to 543 nm of the N -nitroBIPS-DPPG MC moiety suggests that the MC is not exposed to bulk water.…”

“…Together, this suggests that the negatively charged MC moiety is well inserted into the interfacial region of the bilayer, slightly above the carbonyl moieties of the FA esters. It has been previously reported 17, 20 that free MC preferentially associates with bulk water in the presence of zwitterionic 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine (POPC) liposomes, but is able to interact with anionic 1-palmitoyl-2-oleoyl- sn -glycero-3-phospho-(1′- rac -glycerol) (POPG) liposomes. Under the experimental conditions employed herein, the covalently bound MC moiety of N -nitroBIPS-DPPG is rather deeply inserted into the interfacial region of DOPC bilayers.…”

Synthesis, crystal structures, and laser flash photolysis of 3-nitro-7a,15-methanonaphtho[1',2':6,7][1,3]oxazepino[3,2-a]indole derivatives

“…[1][2][3][4] One of the most important classes of chromogenic materials is photochromic 6-nitro-1′,3′-dihydrospiro[chromene-2,2′-indoles], also known in the literature as 6-nitrospiro[2H-1-benzopyran-2,2′-indolines], which have been extensively studied due to their potential applications in various areas of materials science and advanced technologies. [5][6][7][8] The aforementioned compounds under UV-irradiation undergo rapid C-O bond cleavage, converting to the planar, coloured trans-merocyanine form. 9,10 The synthesis of 1′,3′-dihydrospiro-[chromene-2,2′-indoles] is usually based on the condensation of 2-methylideneindoline derivatives with such aryl aldehydes as 5-nitrosalicylaldehyde.…”

Synthesis and Antibacterial Activities of Antibacterial Peptides with a Spiropyran Fluorescence Probe

“…In this context, we planned to prepare photochromic-probe-modified antibacterial peptides to investigate their antibacterial activity and potential use in mechanism studies. The spiropyran compounds are excellent photochromic fluorophores and have been widely used to build functional materials272829303132333435 and chemical sensors36373839 based on the photo-reversible isomerization between two thermodynamically stable states: a colorless spiro-form (spiropyran, Sp ) and a colored open-form (merocyanine, Mc ). Therefore, we envisioned that the introduction of a spiropyran moiety into peptides could be an efficient strategy to study the structure of antibacterial peptides by measuring the change in fluorescence based on the isomerization of spiropyran units in different polar environments40, which further control AMP activity in time and space41.…”