N-Glycosylation profiling of intact target proteins by high-resolution mass spectrometry (MS) and glycan analysis using ion mobility-MS/MS.

Glycosylation influences the structure and functionality of glycoproteins, and is regulated by genetic and environmental factors. The types and abundance of glycans on glycoproteins can vary due to diseases such as cancer, inflammation, autoimmune and neurodegenerative disorders. Due to the crucial role glycans play in modulating protein function, glycosylation analysis could lead to the discovery of novel biomarkers and is of prime importance in controlling the quality of glycoprotein biopharmaceuticals. Here, we present a method for the identification and quantification of glycoforms directly on intact proteins, after immunoaffinity purification from biological fluids. The method was validated and applied to serum transferrin and the biopharmaceutical trastuzumab. The accuracy of the method, expressed as the relative error (RE), ranged from 2.1 (at high concentrations) to 7.9% (at low concentrations), and intra- and inter-day precision, expressed as relative standard deviation (RSD), was 3.2 and 8.2%, respectively. The sensitivity and linearity of the method were suitable for serum analysis and the LOQ was calculated to be 3.1 and 4.4 µg mL-1 for transferrin (TFN) and trastuzumab (TRA), respectively. Its application to transferrin from five healthy human serum samples yielded concentrations between 1.61 and 3.17 mg mL-1, which are in agreement with blood reference levels. In parallel, the structure of the identified glycans was determined by ion mobility spectrometry coupled with tandem mass spectrometry. No chromatographic separation was required and sample preparation was performed in a semi-automatic manner, facilitating the handling of up to 12 samples at a time. This method should be useful for clinical laboratories and for the quality control of large batches of biopharmaceuticals.

Hydroxycinnamic acid amides with oxazole-containing amino acid: synthesis and antioxidant activity.

Three hydroxycinnamic acid derivatives conjugated with glycine-containing oxazole were synthesized. The prepared compounds were tested for their antioxidant activity using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) test. Among the tested hydroxycinnamic acid amides the highest DPPH scavenging activity has been found for the sinapic acid amide.

Cinnamoyl- and hydroxycinnamoyl amides of glaucine and their antioxidative and antiviral activities.

The aporphine alkaloid glaucine has been converted into 3-aminomethylglaucine and its free amino group has been linked to cinnamic, ferulic, sinapic, o-, and p-coumaric acids. The antioxidative potential of the synthesized amides was studied against DPPH(*) test. All of the tested compounds demonstrated higher radical scavenging activity than glaucine and 3-aminomethylglaucine, and lower antioxidative effect than the free hydroxycinnamic acids. The newly synthesized compounds were tested in vitro for antiviral activity against viruses belonging to different taxonomic groups.

Synthesis of cinnamoyl and hydroxycinnamoyl amino acid conjugates and evaluation of their antioxidant activity.

Fifteen amides of cinnamic, ferulic and sinapic acids with natural and unnatural C-protected amino acids have been synthesized. The amides (E)-N-(feruloyl)-L-tyrosine methyl ester (10), (E)-N-(feruloyl)-L-phenylalanine t-butyl ester (11), (E)-N-(sinapoyl)-L-tyrosine methyl ester (13) and (E)-N-(sinapoyl)-L-phenylalanine t-butyl ester (15) with a free carboxyl group of amino acids have been found in nature. The rest of the compounds are unknown. The hydroxycinnamoyl amino acid conjugates have been studied for their antioxidant activity (AOA) in bulk phase lipid autoxidation. The highest AOA has been found for the compounds 11 and 15, which contain the same phenylalanine moiety.