149
hours under room temperature. After maximum consumption of the starting materials as monitored by TLC, the solution was concentrated under reduced pressure. The crude product was purified with column chromatography using silica gel with MeOH/DCM (0-20%): as the solvent gradient system to obtain the white- coloured pure product. The compound was characterized by 1H NMR, 13C NMR and HRMS analyses.
1H NMR (600 MHz, DMSO-d6) δppm 8.72 – 8.25 (brs, 3H), 8.09 – 7.59 (brs, 1H), 7.29 – 7.09 (brs, 8H), 4.60 - 4.42 (s, 8H), 1.54 - 1.49 (m, 2H), 1.47 – 1.42 (m, 4H), 1.35 -1.28 (m, 2H), 1.23 – 1.16 (m, 4H), 0.83 – 0.81 (t, J = 12 Hz, 6H). 13C NMR (150 MHz, DMSO-d6) δppm 154.2, 138.5, 128.6, 127.2, 43.8, 41.5, 31.0, 30.4, 19.7, 14.1. HRMS (ESI) calcd. for C13H17N5O6S2 (M+ H)+ : 435.3231, found: 435.3250.
starting materials the solvent was evaporated under reduced pressure to get the crude product. Reddish-brown coloured pure product was obtained through column chromatography using silica gel with MeOH/DCM (0-20%): as the solvent gradient system. The compound was characterized by 1H NMR, 13C NMR and HRMS analyses.
1H NMR (600 MHz, DMSO-d6) δppm 8.72 – 8.25 (brs, 3H), 8.09 – 7.59 (brs, 1H), 7.29 – 7.09 (brs, 8H), 4.60 - 4.42 (s, 8H), 1.54 - 1.49 (m, 2H), 1.47 – 1.42 (m, 4H), 1.35 -1.28 (m, 2H), 1.23 – 1.16 (m, 4H), 0.83 – 0.81 (t, J = 12 Hz, 6H). 13C NMR (150 MHz, DMSO-d6) δppm 154.2, 138.5, 128.6, 127.2, 43.8, 41.5, 31.0, 30.4, 19.7, 14.1. HRMS (ESI) calcd. for C28H32ClN11O10S4 (M+ H)+ : 435.3231, found: 435.3250.
4.4.2.9. Synthesis of compound 4.2d
To the gently stirring solution of 4.2c (100 mg, 1 equiv.) and KOH (1.5 equiv.) in DMF, was added a DMF solution of 4.7 to the reaction mixture. After maximum consumption of 5.7, the solvent was evaporated under reduced pressure. A 5 mL 3M HCl solution was added to the mixture and the product was extracted three times using EtOAc (3*20 mL) solution. The combined EtOAc extracts were dried over MgSO4 and concentrated under reduced pressure. Brown-coloured pure product was purified through column chromatography using MeOH/DCM (0-30%) as the eluent system. The compound was characterized by 1H NMR, 13C NMR and HRMS analyses.
1H NMR (600 MHz, DMSO-d6) δppm 8.72 – 8.25 (brs, 3H), 8.09 – 7.59 (brs, 1H), 7.29 – 7.09 (brs, 8H), 4.60 - 4.42 (s, 8H), 1.54 - 1.49 (m, 2H), 1.47 – 1.42 (m, 4H), 1.35 -1.28 (m, 2H), 1.23 – 1.16 (m, 4H), 0.83 – 0.81 (t, J = 12 Hz, 6H). 13C NMR (150 MHz, DMSO-d6) δppm 154.2, 138.5, 128.6, 127.2, 43.8, 41.5, 31.0, 30.4, 19.7, 14.1. HRMS (ESI) calcd. for C120H170N14O16S2 (M+ H)+ : 435.3231, found: 435.3250.
4.4.3. UV-Vis Titrations
A 50 µM stock solution of 4.2c was taken in DMSO in a quartz cuvette, and the UV-Vis absorbance spectrum at 298 K was recorded between 250 nm and 550 nm.
Aliquots of the DMSO stock solution of 12.5 mM TBACl were sequentially added to the receptor solution, and the UV-Vis spectra was documented each time. By fitting the obtained values in the bindfit 1:2 model.
4.4.4. Ion transport activity studies
4.4.4.1. Ion transport activity studies using the fluorescence-based assay 4.4.4.1.1. Lucigenin-based ion transport studies
151
EYPC-LUVs lucigenin using NaNO3 as the intravesicular solution was prepared according to earlier mentioned protocol in section 3.4.4.1.
4.4.4.1.2. Ion transport activity across EYPC/CHOL-LUVs lucigenin
Ion transport activity of synthesized macrocyclic compounds across EYPC/CHOL‐LUVlucigenin was performed by following protocol in section 3.4.4.1.
4.4.4.2. HPTS-based selectivity studies 4.4.4.2.1. Anion selectivity studies
4.4.4.2.1.1. Preparation of EYPC-LUVsHPTS
The liposomes were prepared for conducting the HPTS-based anion selectivity experiments as mentioned according to the procedure in section 3.4.4.1 incorporating HPTS dye.
4.4.4.2.1.2. Ion transport activity across EYPC/CHOL-LUVHPTS
The anion transport selectivity for the fluorescence assay, in a clean and dry 3 mL fluorescence cuvette, 2940 µL of 20 mM HEPES buffer containing 225 mM of NaxAy, pH 7.2 (where NaxAy = NaCl, NaBr, NaI, NaClO4 and NaNO3), pH 7.2, 50 µL of the EYPC/CHOL-LUVHPTS and 50 µL of 0.75 M NaOH was added in the cuvette. The cuvette was placed under gently stirring condition for 3 minutes in the fluorescence spectrophotometer (Fluoromax-4 spectrofluorometer, Horiba Scientific, Singapore) which was equipped with an external magnetic stirrer. In this 3 minute approximately 0.6 pH gradient was developed between the intravesicular and the extravesicular solution. The HPTS fluorescence was evaluated as a function of time (λem = 510 nm, λex = 450 nm). At t = 50 s, 10 µL of the anionophore solution was added to initiate the kinetics. The vesicles were completely lysed by adding 20 µL of 20%
Triton X-100 at 450 s, and the fluorescence intensity measurement was continued for a further 50 s.
4.4.4.2.1.3. Quantitative measurement of transport activity from HPTS assay The HPTS fluorescence emission intensity was normalized as 0 and 100 unit for the intensities appearing at t = 0 s and t = 500 s respectively. The ion transport efficiency at t = 450 s (before addition of Triton X-100)
𝑇𝑟𝑎𝑛𝑠𝑝𝑜𝑟𝑡 𝑎𝑐𝑡𝑖𝑣𝑖𝑡𝑦, 𝑇𝐻𝑃𝑇𝑆= 𝐹𝑡− 𝐹0
𝐹∞− 𝐹0 × 100% … … . 𝐸𝑞. −4.3
Ft is the fluorescence intensity measured at t = 450 s (before addition of Triton X-100 solution), F0 is the fluorescence intensity recorded immediately before addition of anionophore (t = 0 s) and F∞ is the fluorescence intensity after addition of Triton X- 100 solution after final vesicle lysis at t = 500 s.
4.4.4.2.2. Cation selectivity studies
4.4.4.2.2.1. Preparation of EYPC-LUVsHPTS
The liposomes were prepared for conducting the HPTS-based cation selectivity experiments as mentioned according to the procedure in section 3.4.4.1.
incorporating HPTS dye.
4.4.4.2.2.2. Ion transport activity across EYPC/CHOL-LUVHPTS
The anion transport selectivity for the fluorescence assay were performed according to section 4.4.4.4.1.2.
4.4.4.3. Ion transport activity studies using the ion-selective electrode-based assay
4.4.4.3.1. Chloride ion efflux studies using chloride-ion-selective electrode (chloride-ISE)
The Cl- ion efflux from the LUVs were measured with the help of ISE. Before starting each set of experiments, the ISE was calibrated using solutions of 1 ppm, 10 ppm and 100 ppm.
4.4.4.3.2. Preparation of EYPC/CHOL-LUV
The LUVs were prepared accordingly as mentioned in section 2.4.4.4.2.
4.4.4.3.3. Chloride efflux study across EYPC/CHOL-LUV
The Cl- efflux studies were studied according to the procedure mentioned in section 2.4.4.4.3.
4.4.4.3.4. Quantitative measurement of transport activity from chloride ISE assay
The Cl─ ion efflux efficiency of the compounds was evaluated according to the procedure mentioned in 2.4.4.4.4.
4.4.4.4. Evidence for mobile carrier mechanism
153 4.4.4.4.1. CHOL dependency assay
The EYPC/CHOL-LUVs for the cholesterol dependency experiment with ISE were prepared according to the procedure mentioned in section 2.4.4.4.2. Three liposomes were prepared with varying cholesterol concentrations (10:0, 8:2, and 6:4) and the chloride efflux was determined with these three lipisomes. The ion transport with these LUVs were carried out according to the procedure mentioned in section 2.4.4.4.3. The chloride ion efflux mediated by anionophore 4.2c from the three types of liposomes were found comparable which indicates the anionophore 4.2c doesn’t form channels across the lipid bilayer.
4.4.4.4.2. Temperature-dependent DPPC assay
For preparing the liposomes 1,2-dipalmitoylphosphatidylcholine (DPPC, in deacidified CHCl3) was taken in a clean and dry sample vial. The rest of the procedure was followed as mentioned in section 3.4.4.1.
4.4.4.5. Regeneration studies using proanionophore
4.4.4.5.1. Fluorescent experiment to study the regeneration of anionophore from proanionophore
For the experiment, in a completely clean fluorescence cuvette, 800 µL of phosphate saline buffer (PBS) was added along with the proanionophore 4.2d (1 mM). The fluorescent spectra of proanionophore was recorded (λex = 410 nm). No prominent fluorescent peak was observed at this time. However, after UV irradiation for 10 secs, 2 minutes, 3 minutes, 5 minutes, 10 minutes, 20 minutes and 30 minutes, a fluorescent peak centered at 513 nm was observed which gradually increased. The peak observed at 513 nm corresponded to the photolabile fluorescent aldehyde formed due to photocleavage of the proanionophore to the photo-moiety and the active anionophore.
4.4.4.5.2. Ion transport studies under photomodulation
4.4.4.5.2.1. Ion transport studies after UV irradiation (405 nm) by the fluorescence-based method
The EYPC/CHOL-LUVHPTS were prepared in accordance with the procedure mentioned in 5.1.1. For the ion transport measurement in a clean and dry 3 mL fluorescence cuvette, 2940 µL of 20 mM HEPES buffer containing 225 mM of NaCl, pH 7.2, 50 µL of the EYPC/CHOL-LUVHPTS and 50 µL of 0.75 M NaOH was added in