Electronic Supporting Information (ESI) Synthesis of BC@mTiO2 Hybrid Nanofibers for Highly Efficient Enrichment and Detection of Phosphopeptides Ruifang Gao†, Xiao Chen†, Chuntao Chen, Rui Shi, Fuzhong Ouyang, Jiazhi Yang, Dongping Sun*, Jian Liu* R. Gao, R. Shi, F. Ouyang, Prof. J. Liu* Institute of Functional Nano & Soft Materials (FUNSOM) Jiangsu Key Laboratory for Carbon-based Functional Materials & Devices Soochow University, Suzhou, Jiangsu Province, China X. Chen, C. Chen, Dr. J. Yang, Prof. D. Sun* Institute of Chemicobiology and Functional Materials, School of Chemical Engineering, Nanjing University of Science and Technology, 200 Xiao Ling Wei Street, Nanjing, Jiangsu Province, China † These authors contribute equally to this manuscript. Correspondence: jliu@suda.edu.cn, sundpe301@163.com Tel: 86-512-65884565

500 nm 200 nm 50 nm 20 nm a b c d Fig. S1 TEM images of bare BC nanofibers under different magnification. (a) An overview of the BC nanofibers; (b-c) A zoomed-in view of BC nanofibers; (d) A single BC nanofibers.

Ti Fig. S2 Energy-dispersive spectroscopy (EDX) spectra of the BC@mTiO2 hybrid nanofibers.

Fig. S3 MALDI-TOF mass spectra of the tryptic digest mixture of β-casein and BSA (1:1, w/w) before enrichment.

(a) (b) (c) Fig. S4 (a-c) MALDI-TOF mass spectra of the digest of -casein by the pre-treated BC@mTiO2 tips. Dilution series: 1X, 0.1X, 0.01X respectively, and loading amount for (c): 17 pmol. The phosphorylated fragments and their de-phosphorylated counterparts indicated by * and #, respectively.

(a) (b) (c) Fig. S5 (a-c) MALDI-TOF mass spectra of the enriched samples from a mixture of analytes in a series of mass ratios including1:1; 1:10; 1:100 of digested -casein and BSA, using the pre-treated BC@mTiO2 tips. The phosphorylated fragments and their de-phosphorylated counterparts indicated by * and #, respectively.

(a) (b) Fig. S6 (a) The standard calibration curve using the BCA protein colorimetric detection kit. (b) The measurements of the enrichment capacity of three different materials, including post-treated BC@mTiO2 nanofibers, pre-treated BC@mTiO2 nanofibers, and the commercial TiO2 tip. Error bar: standard deviation (n=3).