BIOMEDICAL APPLICATIONS III: DELIVERY OF IMMUNOSTIMULANTS AND VACCINES - Carbon Nanotubes: From Bench Chemistry to Promising Biomedical Applications - page 88

1) ( CH 2 O) n , DMF

+

Cl -

O NH 3

O

O NH Bo c

N

HO O C N

H

O

120°C, 3 days

2) HC l

1

2

1 ) Bo c-L ys (B o c)- Gly- Ty r(t- bu t)-T yr (t-b u t)-Gly -OH
HATU, D IEA, DMF, 2 hours
2) TFA, 2.5 hours

O N H -C O -G ly -T yr-T y r-G ly -L ys

O

N

3

Scheme 4.1 Functionalisation of CNTs via fragment condensation.

Another characterisation became feasible after the incorporation of
N 15 -labelled Gly at the C-terminal part of the sequence, which allowed for a
homonuclear and heteronuclear two-dimensional (2D) NMR analysis to be
performed. A broad correlation peak in the decoupled 15 N- 1 H spectrum of the
fully protected compound 3 , showing a maximum peak height at 119.6/7.40
ppm, was indicative of a uniform distribution of the peptide around the
nanotubes' sidewall. A series of bi-dimensional experiments then permitted
all the resonances of the peptide moiety to be assigned (Fig. 4.2). A decrease
in and a broadening of the signal intensities were observed for the amino acid
residues approaching the aromatic tube walls. All the predictable sequential
RH i -NH i +1 cross peaks were conirmed in the ROESY spectrum. Moreover, a
spatial correlation between the RH of glycine at position 5 and the amide
proton of the triethylene glycol chain conirmed the presence of a covalent
bond between the peptide and the CNTs (Fig. 4.2b).

Figure 4.2 Partial (a) TOCSY and (b) ROESY 1 H NMR spectra of peptide-CNT 3 in
H 2 O/ t -BuOH- d 9 (9:1) solution. Peptide residues are numbered from Lys1 to Gly5. TEG
denotes triethylene glycol. The TOCSY spectrum was recorded while decoupling the
15

N heteronucleus. Reproduced from Pantarotto et al. 5 with permission.