S1

Supporting Information

Gold-Induced Unfolding of Lysozyme: Towards the Formation of Luminescent

Clusters

Debasmita Ghosh,1†

Ananya Baksi,1†

Sathish Kumar Mudedla,2 Abhijit Nag,

1 Mohd Azhardin

Ganayee,1 Venkatesan Subramanian

2 and Thalappil. Pradeep

1*

1DST Unit of Nanoscience (DST UNS) & Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai-600036, India

2Chemical Laboratory, CSIR-Central Leather Research Institute, Adyar, Chennai- 600020

Email: pradeep@iitm.ac.in

Table of Contents

Number Description Page Number

S1 The structures of Lyz at pH 5.5 and 7 S3

S2 ESI MS/MS of Lyz and Au2-Lyz at different collision energy S4

S3 Infrared (IR) spectra Lyz and Aun-Lyz complexes at different

Lyz:Au ratio

S5

S4 Original IR spectra and second derivative spectra of Lyz and

Aun-Lyz complexes at different Lyz:Au ratios

S6

S5 Simulated structures of Lyz S7

S6 Simulated structures of Au2-Lyz S8

S7 Simulated structures of Au4-Lyz S9

S8 Simulated structures of Au6-Lyz S10

S9 Simulated structures of Au8-Lyz S11

S10 Residue-wise calculated secondary structure of Lyz at pH

5.5.

S12

S11 Residue-wise calculated secondary structure of Au2-Lyz and

Au4-Lyz

S13

S12 Residue-wise calculated secondary structure of Au6-Lyz and

Au8-Lyz

S14

S13 Root mean square fluctuation of Lyz and Au8-Lyz S15

S2

ESI MS measurements

To get the well resolved mass spectrum for CIU and CID experiments in ion mobility (ESI IM-

MS) mode, the following instrumental parameters were used:

Sample concentration: 1µg/mL

Solvent: Water

Flow rate: 10-20 µL/min

Capillary voltage: 2-3 kV

Cone voltage: 50V

Source offset: 0 V

Desolvation gas flow: 700 L/h

Trap gas flow: 2 mL/min

He gas flow: 180 mL/min

Ion mobility gas flow: 90 mL/min

Bias voltage: 45 V

Wave velocity: 600 m/s

Wave height: 40 V

S3

Figure S1: The structures of Lyz at pH 5.5 (cyan) and 7 (blue).

S4

Figure S2: (A) ESI MS/MS of Lyz at different collision energies, showing fragmentation of the

protein. (B) ESI MS/MS of Au2-Lyz at different collision energies. Fragmentation is more facile

in case of Au2-Lyz.

200 400 600 800 15001000200 400 600 800 1000 1500

m/z m/z

70

80

85

90

Lyz Au2-LyzA) B)

S5

Figure S3: Infrared (IR) spectra of Lyz and Aun-Lyz complexes at different Lyz:Au ratio.

1000 2000 3000 400020

30

40

50

60

70

Lyz

1:10

1:5

1:4

Wavenumber (cm-1)

Inte

nsi

ty

S6

Figure S4: Original IR spectra (black) and second derivative spectra (red) of the Lyz (A) and

Aun-Lyz complexes at different Au: Lyz ratios (B) 1:1.5, (C) 1:3 and (D) 1:4.

1700 1680 1660 1640 1620 1600-0.5

0.0

30

40

1700 1680 1660 1640 1620 1600-0.5

0.0

50

60

1700 1680 1660 1640 1620 1600

0

60

1700 1680 1660 1640 1620 1600

0

40

50

60

Wavenumber (cm-1)Wavenumber (cm-1)

Wavenumber (cm-1)Wavenumber (cm-1)

A) B)

C) D)

Lyz 1:1.5

1:3 1:4

S7

Figure S5: Simulated structure of Lyz.

S8

Figure S6: Simulated structure of Au2-Lyz.

S9

Figure S7: Simulated structure of Au4-Lyz.

S10

Figure S8: Simulated structure of Au6-Lyz.

S11

Figure S9: Simulated structure of Au8-Lyz.

S12

Figure S10: Residue-wise calculated secondary structure of Lyz at pH 5.5.

S13

Figure S11: Residue-wise calculated secondary structure of Au2-Lyz (A) and Au4-Lyz (B).

S14

Figure S12: Residue-wise calculated secondary structure of Au6-Lyz (A) and Au8-Lyz (B).

S15

Figure S13: Root mean square fluctuation for Lyz (black trace) and Au8-Lyz (red trace).

0 20 40 60 80 100 120 1400.0

0.1

0.2

0.3

0.4

0.5

RM

SF

(n

m)

Residue No.