Racheal Spruill (UMBC)

Mentor: Dr. Susana Teixeira

SURFing with Green Tea:

What Neutrons Read

in Tea Leaves
BSA & Polyphenols

High Pressure

Neutron Scattering

Experimental Setup

Results

Conclusion & Future Directions

OUTLINE

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Electrostatic Potential (mV) 

Calculated using Adaptive Poisson-Boltzmann Solver (APBS) at pH 7. 

[Baker et al. (2001). PNAS 98, 10037-10041]

Bovine Serum Albumin

• MW = 66 kDa

• pI = 5.3

• Buffer for our studies: 

100 mM MES pH 6.5, 50mM KCl
Computational 

docking analysis 

binding sites

(+)-Catechin (-)-Epigallocatechin Gallate (EGCG) Interactions

Hydrophobic

(VDW + Nonpolar)

-25.11 kCal/mol (EGCG)

-18.63 kCal/mol (Catechin)

Hydrogen bonding 7.49 (EGCG) 

1.68 (Catechin)

[Tang et al. (2017). J. Agric. Food Chem. 65: 656-665]

~84 Å

~47 Å

Green Tea Polyphenols
No Treatment

High Pressure Effects

Adapted from: R. Winter et al. (2007). J. Non-Equilib. Thermodyn. 32, 41–97.

Protein Volume = Vindividual atoms + Vinternal cavities + Vsolvation

+P +P TEM images of Green Tea leaves; adapted from Scepankova et al. (2018). Plant Foods for Human Nutrition 73: 253-267.

Higher yields of polyphenols

Increased antioxidant activity

4 kbar

20 kbar

High Pressure High Temperature

1 μm 1 μm 1 μm
Why SANS?

Adapted from Teixeira et al. (2018) J. Neutron Res. 20(1), 13-23. 

Pressure: up to 3.5 kbar. 

Temperature : -15°C to +65°C

q-Range: 0.001-0.3 Å-1

Sample Volume: 2.5 mL per load.

Typical Sample: 3-10 mg/mL

Structure, conformation of biomaterials Function and behavior 

2θ =15°

Reciprocal space 

Real space
GOALS

Investigate:

•Structure and stability of 

BSA-polyphenol 

complexes under 

conditions relevant to 

food processing

•Effects of pressure on 

conformation and 

binding of polyphenols 

to BSA

Adapted from Hiperbaric High Pressure Processing.

Up to 6kbar
Concentration Screening & Structure Factor

II qq − BB

SANS (NG7 & NGB30 instruments) SAXS (IBBR In-House Source)
BSA Ellipsoid Model - Rough Fitting

[Protein] a

Minor Eq. Radius (Å)

b

Major Eq. Radius (Å)

c

Polar Radius 

(Å)

20 mg/ml 42.6 ± 0.3 49.5 ± 0.3 17.7 ± 0.1

40 mg/ml 37.7 ± 0.1 64.9 ± 1.3 17.0 ± 0.1

Tri-axial model: Finnigan, J.A., Jacobs, D.J., 1971. J. Phys. D: Appl. Phys. 4, 72-77. 

Hayter MSA Structure Factor model: J B Hayter & J Penfold, 1981. Molecular Physics 42, 109-118.

II qq = PP qq ∗ SS qq
Complexes of Polyphenols/BSA – Parameters Probed

EGCG EGCG CAT

Parameters

BSA Concentration 10 mg/mL – 60 mg/mL

Molar Ratio (Polyphenol: BSA) 0 – 30 mol

Time 2 hrs – 4 weeks

H2O/D2O Solvation 100% H2O – 100% D2O 
Catechin vs EGCG Effects on BSA Structure – SAXS and CD Data

SAXS data collected at the IBBR in-house source: SAXSLAB Ganesha 300 XL with a Rigaku source.

Chirascan Solutions using Reference Data #7: CD spectrometer (IBBR), Sreerama Applied , N. and Woody, R.W. Photophysics. Path length = 0.1 m (2000), Analytical Biochemistry, 287, 252–260. 

Circular Dichroism
HP-SANS – 20 & 40 mg/mL BSA Complexed with EGCG
Conclusions

 Established the onset of S(q) for BSA solutions

 Established SAS profiles for BSA/polyphenol complexes 

 Determined the effects of polyphenols on the secondary structure of BSA

 Determined the effects of HP on the complex structure

 Established the use of HP SANS as a viable tool to monitor the effects and their 

reversibility of HP in situ
Future Directions

 Molecular Dynamics (MD) on the 

BSA crystal structure to determine 

models for the solution structure of 

the protein at different pressures

 Near-UV (250-320 nm) CD profiles 

of complexes under HP-SANS 

conditions to monitor binding effects 

on specific types of amino acids and 

disulfide bonds

 Probe HP effects vs Temperature, pH
Acknowledgements

 NSF - CHRNS

 Susana Teixeira (SURF Mentor, U. Delaware/NIST)

 Amy Xu (IBBR/NIST)

 Alex Grishaev (IBBR) 

 Joe Dura & Julie Borchers (NIST)

 NCNR Neutron Condensed Matter Science Group 

 Fellow SURFers (Shark Tank, Fish Bowl, Submarine, & 

the Exiles)

THANK YOU!!!