Supplementary Figure 1. Structure of BSA modeled (SWISS-MODEL workspace
) using the X-ray structure of HSA (PDB entry: 1E78) as a template. The figure
was generated using PyMol . Amine and hydroxyl groups of lysil and seryl side-
chains, which were the primary targets for conjugation of the surface modifiers, are
marked in red. Only groups that are ≥25% surface-exposed (calculated using CSU
) were used in the analysis.
Supplementary Figure 2. Representative mass spectra of (FITC-labeled) BSA
modified by each of the four amino acid analogues used in this study (Trp, Phe, Leu,
and Ser), along with the spectrum of the non-modified protein. Intact molecular mass
measurements were performed on a Bruker Reflex III matrix-assisted laser
desorption/ionization time-of-flight (TOF-MALDI) mass spectrometer (Bruker)
equipped with delayed ion extraction, reflector, and a 337 nm nitrogen laser. Each
spectrum was generated from accumulated data of 200 laser shots. The error
associated with the measurements is estimate to be within 0.1-0.5%.
Supplementary Figure 3. Characterization of BSA molecules modified by amino
acid analogues. (A) Far-UV CD spectra of BSA and of BSA molecules modified by
each of the analogues used in this study to the largest extent. Spectra were recorded
on Chirascan spectropolarimeter (Applied Photophysics) calibrated with ammonium
d-10-camphorsulfonate in 0.1-mm path-length quartz cuvettes, using a step size of 0.3
nm, a bandwidth of 1 nm, and a time constant of 1 s. As evident, the secondary
structure of the protein is not altered by the conjugation. (B) Size-exclusion
chromatographs of the above BSA species. Samples were run on Superdex 75 at 0.5
ml/min, using PBS as a mobile phase. A 40-kDa dextran (left-hand peak), which has a
hydrodynamic radius about 1 nm larger than that of native BSA, was added as an
internal reference. Differences in size affected by conjugation of the modifiers are
Supplementary Figure 4. Nuclear import of BSA molecules modified by
hydrophobic amino acid analogues into Xenopus laevis oocytes nuclei. Confocal
images of isolated Xenopus oocyte nuclei (obtained as described  in MOCK buffer
(90 mM KCl, 100 mM NaCl2 mM MgCl2, 0.75 mM CaCl2, 1.1 mM EGTA, 10 mM
Hepes, 125 mM sucrose, and protease inhibitors) containing native or modified BSA.
Images were taken 60 min after the introduction of the BSA probes.
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