Mercury vx 300 spectrometer

¹H nuclear magnetic resonance (¹H NMR) spectra were recorded with a Mercury VX-300 spectrometer (300 MHz, Varian, Palo Alto, CA, USA). Fourier transformed infrared (FTIR) spectra were recorded on a Nicolet 6700 (Thermo Fisher, Hampton, NH, USA). The molecular weights and the molecular weight distributions of the obtained mPEG-PAAHPs were evaluated by size-exclusion chromatography-multi angle light scattering (SEC-MALLS, Milford, MA, USA) system consisted of a Waters 2690D separations module, a Waters 2414 refractive index detector (RI) and a Wyatt DAWN EOS MALLS detector. DMF containing 10 mM LiBr was used as the mobile phase at a flow rate of 0.3 mL/min at 30 °C. The data were processed with Astra software (Wyatt Technology, Santa Barbara, CA, USA).
Temperature responsive behaviors of mPEG-PAAHPs were evaluated by a transmittance measurement at 500 nm (Perkin-Elmer Lambda Bio 40 UV/Vis spectrometer, Hebron, KY, USA) and dynamic light scattering (DLS) (Nano ZS ZEN3600, Malvern Instruments, Westborough, MA, USA). The morphology of the nanoparticles was determined by DLS with a fixed scattering angle of 173° and by transmission electron microscopy (TEM). In this study, the cloud point (CP) was defined as the temperature corresponding to a 10% reduction in the initial transmittance of the solution.

All reactions were carried out using commercially available starting materials or reagents unless otherwise stated. Optical rotations were measured on a WZZ-3A automatic polarimeter (Shanghai YiCe Apparatus & Equipment co. LTD, Shanghai, China), NMR spectra were recorded on a Varian Mercury VX 300 spectrometer (Varian, Tokyo, Japan) or Bruker 400 MHz spectrometer (Bruker, Berlin, Germany) using TMS as an internal standard, and the chemical shifts were reported in ppm relative to CDCl₃ (δ_H 7.26 and δ_C 77.16). High resolution mass spectra (HRMS) were performed on a QSTAR XL mass spectrometry system (Applied Biosystem Co., Foster City, CA, USA) or on a TripleTOF 6600 mass spectrometer (ABSciex, Redwood City, CA, USA). Column chromatography (CC) was performed with silica gel (230–400 mesh, Merck, Darmstadt, Germany). TLC was carried out with an aluminum sheet precoated silica gel G₆₀ (Merck, Darmstadt, Germany). Spots were visualized under UV light or by spraying with 5% H₂SO₄ in EtOH followed by heating.

Melting points were determined on an Electrothermal^® melting point apparatus (Cole-Parmer, Vermon Hills, IL, USA) and are uncorrected. ¹H-NMR spectra were obtained on a Mercury VX-300 spectrometer (Varian, Palo Alto, CA, USA), using deuterochloroform (CDCl₃) as the solvent. Most chemicals were purchased from Acros Organics (Fair Lawn, NJ, USA) and TCI America chemicals (Portland, OR, USA). Mass spectrometry was performed utilizing a VG Analytical 70 S magnetic sector mass spectrometer (Waters, Milford, MA, USA). Chromatography was performed using Geduran^® silica gel (40–63 µm).

The ¹H NMR spectra of peptide and peptide-based bis-acrylate were characterized using DMSO-d6 as solvents (Mercury VX-300 spectrometer, Varian, Palo Alto, CA, USA). FTIR spectra of freeze-dried hydrogels were characterized using the KBr method (AVATAR 360 spectrometer, Nicolet, Madison, WI, USA).