Biospin avance 3

NMR
spectra were recorded
on a Bruker BioSpin AVANCE III (500 and 400 MHz for ¹H,
125 MHz for ¹³C) instrument in the indicated solvent. Chemical
shifts are reported in parts per million (ppm) relative to the signal
(0.00 ppm) for internal tetramethylsilane for solutions in CDCl₃ (7.26 ppm for ¹H, 77.16 ppm for ¹³C).
Multiplicities are reported using the following abbreviations: s,
singlet; d, doublet; dd, doublet of doublets; t, triplet; q, quartet;
m, multiplet; br, broad; J, coupling constants in
hertz. IR spectra were recorded on a JASCO FT/IR-4200 spectrometer.
Only the strongest and/or structurally important peaks are reported
as IR data given in cm^–1. Mass spectra were measured
using a Bruker micrOTOF II. HRMS (ESI-TOF) was calibrated using sodium
formate. All reactions were monitored by thin-layer chromatography
carried out on 0.2 mm E. Merck silica gel plates (60F-254) with UV
light (254 nm). Column chromatography was performed on Silica Gel
60 N, purchased from Fuji Silysia Chemical Ltd. 4-Propargylaminoisoxazoles 8 and isoxazolopyridines 9 and 10 were prepared in accordance with the previously reported procedure.^{19 (link)} Spectral data for 8i and 9i (newly prepared compounds) are shown below.

PLL aqueous solution
(10 mmol, 25 wt %) was placed in a glass vial, and the pH was adjusted
to 7 by adding a small amount of HCl; then, 2 mmol of 2-iminothiolane
was added to give a substitutional ratio of 20% for the thiol group.
The aqueous solution was mixed using a magnetic stirrer bar for 2
h at room temperature. Then, the products were obtained following
dialysis for 2 days using the dialysis membrane (molecular weight
cutoff of 500) and freeze-drying for 2 days. The substitutional ratio
of the thiol group was calculated from the ¹H NMR spectrum
of the polymer sample. The ¹H NMR spectrum of PLL-SH dissolved
in D₂O was recorded at 25 °C using a 400 MHz NMR spectrometer
(BioSpin AVANCE III, Bruker, Billerica, USA). The zeta potential of
PLL-SH was determined by plotting the zeta potential against pH. The
zeta potential of PLL-SH dissolved in pure water (1 mg/mL) was measured
using a Zetasizer Nano ZS ZEN3600 (Malvern Instruments Ltd., Malvern,
UK) instrument. To tune the pH of the polymer solution (1 mL), a small
amount of HCl or NaOH was added. These measurements were repeated
several times, and the average and standard deviation were estimated
for each pH.