A novel preparative strategy of both α-MMC and MAP30 at one time was successfully established. Some properties of these proteins were assessed by SDS-PAGE, ESI-QUAD-MS, MALDI-TOF-MS, and N-terminal sequence as well as Western blotting. This fast, highly efficient methodology enables us to focus more energy on subsequent research. A branched (mPEG) 2 -Lys-NHS(20 kDa) was used to modify these proteins and the serial PEGylated ones were assessed by gradient SDS-PAGE and MALDI-TOF-MS. The α-MMC modifier possessed one-mer, two-mer, and three-mer PEGbound chains, while MAP30 modifier obtained one-mer and two-mer PEG-bound chains. PEGylated conjugates preserved moderate activities on JAR choriocarcinoma cells and HSV-1. Furthermore, both PEGylated proteins showed about 60%-70% antitumor and antivirus activities as well as a 50%-70% immunogenicity decrease when compared with unmodified counterparts. To sum up, PEGylation of α-MMC and MAP30 may offer a possible way for their clinical application as potential therapeutic agents. Nevertheless, to fulfill the requirements of a useful drug, we should meet the challenges, including the reduction of immunogenicity to the greatest extent, the retention of sufficient activity, the extension of the half-life period, and development of various forms of PEG-RIPs. This work is just the beginning for them to be used clinically. After all, therapeutic proteins must fulfill the requirements described previously. PEGylation can reduce immunogenicity and retain certain biological activity of RIPs, but there is lots of work to do for further decreasing their immunogenicity and extending the half-life period. The International Journal of Nanomedicine is an international, peerreviewed journal focusing on the application of nanotechnology in diagnostics, therapeutics, and drug delivery systems throughout the biomedical field. This journal is indexed on PubMed Central, MedLine, CAS, SciSearch®, Current Contents®/Clinical Medicine, Journal Citation Reports/Science Edition, EMBase, Scopus and the Elsevier Bibliographic databases. The manuscript management system is completely online and includes a very quick and fair peer-review system, which is all easy to use. Visit http://www.dovepress.com/ testimonials.php to read real quotes from published authors.