Finnigan lcq

All melting points were taken on an X-6 microscope melting point instrument (Bjfuka, Beijing, China) and are uncorrected. Infrared spectra were determined with a TENSORII spectrometer (Bruker, Karlsruhe, Germany). NMR spectra were measured using 300 MHz Bruker AV III spectrometers (Bruker, Karlsruhe, Germany) and 400 MHz JNM-ECZ400S/L1 spectrometers (Varian INOVA, Palo Alto, CA, USA) with tetramethylsilane (TMS) as an internal standard. The following abbreviations were used to designate the multiplicities: s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, brs = broad singlet. Coupling constant (J) is reported in Hertz (Hz). HR-MS spectra were obtained on Finnigan LCQ and Micromass Auto Spec Ultima-Tof spectrometer (Thermo, Boston, Massachusetts, USA). Analytic thin-layer chromatography (TLC) was performed on precoated silica gel 60 F254 plates (Qingdao Haiyang, Qingdao, Shandong Province, China) using petroleum ether-ethyl acetate as solvent system. All the chemicals were of analytic grade. The detailed preparation procedures of intermediates, byproducts, and target compounds are described below.

All elastin samples were totally hydrolyzed and further treated and analyzed as previously described in Heinz et al. (27 (link)). In brief, liquid chromatography (LC)–MS analysis of desmosine and isodesmosine was carried out using an Agilent 1100 LC system (Agilent Technologies, Santa Clara, CA, USA) coupled to a quadrupole ion trap mass spectrometer (Finnigan LCQ; Thermo Fisher Scientific) with an electrospray interface operated in the positive ion mode.

ESI-MS analysis was performed using a Finnigan LCQ ion trap mass spectrometer (Thermo Fisher Scientific Inc., San Jose, CA, USA). The degradation media containing degradation products were frozen and lyophilized. Then samples were dissolved in chloroform and PCANs were removed via filtration. The solutions of degradation products were dissolved in a chloroform/methanol (1:1 v/v) system and were introduced to the ESI source via continuous infusion using the instrument syringe pump at a rate of 5 µL/min. The ESI source of the LCQ was operating at 4.5 kV, and the capillary heater was set to 200 °C. Nitrogen was used as the nebulizing gas. The analyses were performed in negative-ion mode.

Pure elastin, free of contaminants by other ECM components, was isolated from biopsies of mouse lung as described previously (Schmelzer et al., 2012 (link)). Isolated elastin samples were weighed and then hydrolyzed at a concentration of 1 mg/ml in 6 M HCl at 105°C for 24 hours, respectively, to allow the liberation of DES and IDES. After incubation, the samples were evaporated to dryness at 60°C, and the residues were taken up in acetonitrile:water (1:1, v/v) prior to liquid chromatography mass spectrometry (LC-MS) analysis. LC-MS analysis of DES and IDES was carried out using an Agilent 1100 LC system (Agilent Technologies, Waldbronn, Germany) coupled to a quadrupole ion trap mass spectrometer Finnigan LCQ (Thermo Fisher Scientific, Waltham, MA) by an electrospray interface. Isocratic chromatographic separation was performed over 8 minutes at a flow rate of 0.2 ml/min on a Reprosil-Pur 120 C18 AQ 3 μm column (150×2 mm, Maisch, Ammerbuch-Entringen, Germany). 0.1% formic acid/methanol (97.5:2.5, v/v) was used as the mobile phase and the column temperature was 40°C. Under these chromatographic conditions DES and IDES co-elute. For mass spectrometric analyses, the following parameters were used: positive ion mode, electrospray voltage: 4.5 kV, heated capillary temperature: 220°C.