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Table 2 Peptide sequences of LXY1 derivatives (cyclic cdGX1G-Hyp-X3cX4) and their binding affinities against U-87MG cells

From: Discovery and characterization of a high-affinity and high-specificity peptide ligand LXY30 for in vivo targeting of α3 integrin-expressing human tumors

 

X1

X2

X3

X4

Relative binding index

IC50 (μM)

LXY1

L

G

N

 

1.00 ± 0.05

3.5 ± 0.4

LXY4

Phe(3,5-diF)

G

N

 

1.36 ± 0.11

0.41 ± 0.03

LXY5

Phe(3,4,5-triF)

G

N

D-T

1.45 ± 0.12

ND

LXY6

Phe(3,5-diF)

G

N

W

1.17 ± 0.08

ND

LXY7

Phe(3,4,5-triF)

G

N

R

1.62 ± 0.10

0.13 ± 0.012

LXY8

L

G

N

D

0.22 ± 0.03

ND

LXY9

Phe(3,5-diF)

G

N

D-S

1.44 ± 0.11

ND

LXY10

L

G

D

G

0.64 ± 0.05

ND

LXY11

Phe(3,4-diF)

G

N

D-K

1.01 ± 0.10

ND

LXY12

Phe(3,4-diF)

G

N

S

0.47 ± 0.05

ND

LXY13

Phe(3,4,5-triF)

G

N

D

0.57 ± 0.03

ND

LXY14

Phe(3,4,5-triF)

G

N

D-S

1.35 ± 0.09

ND

LXY15

Phe(3,5-diF)

G

N

D-K

1.31 ± 0.08

ND

LXY16

Phe(3,5-diF)

G

N

S

0.61 ± 0.05

ND

LXY17

Phe(3,4-diF)

G

N

G

0.65 ± 0.06

ND

LXY18

Phe(3,4-diF)

G

N

W

0.01 ± 0.008

ND

LXY19

Phe(3,5-diF)

G

S

 

0.84 ± 0.07

ND

LXY20

L

G

D-Thi

 

0.15 ± 0.02

ND

LXY21

Phe(3,5-diF)

G

Y

 

0.62 ± 0.04

ND

LXY22

L

G

R

 

0.93 ± 0.1

ND

LXY23

L

G

Orn

W

0.7 ± 0.06

ND

LXY29

Phe(3,4-diF)

G

N

R

1.59 ± 0.09

ND

LXY30

Phe(3,5-diF)

G

N

R

1.68 ± 0.10

0.08 ± 0.01

LXY32

L

G

N

R

0.94 ± 0.07

ND

LXY33

OLeu1

G

N

R

0.81 ± 0.1

ND

LXY34

N- [(3,4,5-triF)benzyl]Gly2

G

N

R

0.68 ± 0.06

ND

LXY36

Phe(3,4,5-triF)

G

N

D-R

1.39 ± 0.10

ND

LXY37

L

G

N

D-R

0.67 ± 0.06

ND

LXY38

Phe(3,5-diF)

G

N

D-R

0.69 ± 0.05

ND

LXY39

Phe(3,5-diF)

Aoa3

N

D-R

1.09 ± 0.09

ND

  1. 1: 2: 3:
  2. Phe(3,4,5-triF) 3,4,5-trifluorophenylalanine, Aad α-aminohexanedioic acid, Aoa aminooxy acetic acid, ND not determined
  3. Relative binding index (RBI) of each peptide was determined as described below. Peptide at 0.4 μM was used to compete for the binding of 0.5 μM LXY1-biotin to U-87MG cells, followed by incubation with streptavidin-PE before analyzing by flow cytometry. Mean fluorescence intensity (MFI) was used as a quantitative measurement. The RBI for each sample was determined by the following formula: (MFI of positive control − MFI of the sample)/(MFI of positive control − MFI of LXY1). Positive control: 0.5 μM of LXY1-biotin. The peptide with greater RBI has higher binding affinity. When IC50 of the peptide was determined, the tested peptide with a series of concentration competed with 0.5 μM LXY1-biotin binding to U-87MG cells