Table 1 The letter and secondary structural element (SSE) frequency distributions and 2-sample T-tests of first-and second-shell amino acid residues vs. all amino acid residues in the Mg²⁺-proteins

Letter, x^a

ν_x,1/ν_{x, all}^b

T-test^c

p-value^c,d

ν_x,2/ν_{x, all}^e

T-test^c

p-value^c,d

a

1.47

1.4037

0.0802

0.57

2.4731

0.0067

b

1.86

2.7909

0.0027

1.20

1.2200

0.1113

c

0.56

2.0160

0.0219

0.50

4.3510

<0.0001

d

1.23

1.7376

0.0412

1.23

3.1829

0.0008

e

1.46

1.0111

0.1560

2.03

4.1825

<0.0001

f

1.47

1.9389

0.0263

1.70

5.4060

<0.0001

g

1.15

0.2494

0.4015

1.18

0.5381

0.2953

h

5.29

9.3752

< 0.0001

1.19

0.7921

0.2142

i

0

1.8928

0.0292

1.34

1.1910

0.1168

j

2.21

1.6156

0.0531

1.54

1.3401

0.0901

k

1.40

1.4992

0.0669

1.60

4.1820

<0.0001

l

0.76

0.9209

0.1786

1.08

0.5978

0.275

m

0.52

2.9377

0.0017

0.74

5.2192

<0.0001

n

0.53

1.1306

0.1291

0.88

0.5208

0.3013

o

1.52

1.4066

0.0798

0.35

3.3637

0.0004

p

0

3.1174

0.0009

0.77

1.3204

0.0934

SSE, x

Loop

1.56

2.5575

0.0053

1.47

2.1874

0.0144

β-strands

1.30

1.0780

0.1405

1.34

1.2170

0.1118

α-helices

0.47

3.6454

0.0002

0.51

3.3621

0.0004