title: Quantitative assessment of preloaded 4-alkoxybenzyl alcohol resins for solid-phase peptide syntheses by 1D and 2D HR-MAS NMR.
abstract: The quality of preloaded Wang resins is very important for the success of solid-phase peptide syntheses (SPPS). A critical factor is the capping of remaining hydroxyl groups after loading with the first amino acid, since these free alcohols lead to truncated sequences during the following SPPS steps. Because the detection of hydroxyl groups by color tests is difficult and unreliable, the capping efficiency is often controlled by time-consuming peptide test syntheses. Here, we describe a two-dimensional, high resolution magic angle spinning NMR method for the quantitative determination of remaining 4-alkoxybenzyl alcohols in Fmoc-Xaa-Wang resins with a detection limit of 1 mol-%. The NMR method was validated with samples of known ratios between Fmoc-Ala-Wang and 4-alkoxybenzylalcohol resin. Application to a set of preloaded Fmoc-Ala- and Fmoc-Thr(tBu)-Wang test resins demonstrated that the full range of essential amino acids can be quantified without further spectrometer calibration. Compared to established test synthesis protocols, the NMR method represents not only advantages in terms of time and cost savings but also eliminates all inaccuracies due to further sample treatment like SPPS and cleavage from the resin.
authors.affiliation: Swiss Federal Laboratories for Materials Science and Technology (Empa) , Laboratory for Functional Polymers, Überlandstrasse 129, CH-8600 Dübendorf, Switzerland.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rentsch
authors.forename: Christian
authors.initials: C
authors.lastname: Stähelin
authors.forename: Markus
authors.initials: M
authors.lastname: Obkircher
authors.forename: Roland
authors.initials: R
authors.lastname: Hany
authors.forename: Marina
authors.initials: M
authors.lastname: Simeunovic
authors.forename: Daniel
authors.initials: D
authors.lastname: Samson
authors.forename: Günther
authors.initials: G
authors.lastname: Loidl
authors.forename: Fritz
authors.initials: F
authors.lastname: Dick
mesh_terms: D001592:Benzyl Alcohols / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010455:Peptides / Q000138:chemical synthesis*; D060327:Solid-Phase Synthesis Techniques
chemical_list: D001592:Benzyl Alcohols; D010455:Peptides