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Succinimidyl ester surface chemistry: implications of the competition between aminolysis and hydrolysis on covalent protein immobilization.

Lim CY, Owens NA, Wampler RD, Ying Y, Granger JH, Porter MD, Takahashi M, Shimazu K - Langmuir (2014)

Bottom Line: The hydrolysis of the DSP-based monolayer is proposed to follow a reaction mechanism with an initial nucleation step, in contrast to a simple pseudo first-order reaction rate law for the entire reaction, indicating a strong dependence of the interfacial reaction on the packing and presence of defects in the adlayer.This interpretation is used in the subsequent analysis of IR-ERS kinetic plots which give a heterogeneous aminolysis rate constant, ka, that is over 3 orders of magnitude lower than that of the heterogeneous hydrolysis rate constant, kh.This result is paramount for biosensors that use NHS chemistry for protein immobilization due to effects that may arise from noncovalently linked proteins.

View Article: PubMed Central - PubMed

Affiliation: Departments of Chemical Engineering, ‡Chemistry, §Bioengineering, and ∥Pathology and the ⊥Nano Institute of Utah, University of Utah , Salt Lake City, Utah 84112, United States.

ABSTRACT
N-Hydroxysuccinimide (NHS) ester terminal groups are commonly used to covalently couple amine-containing biomolecules (e.g., proteins and peptides) to surfaces via amide linkages. This one-step aminolysis is often performed in buffered aqueous solutions near physiological pH (pH 6 to pH 9). Under these conditions, the hydrolysis of the ester group competes with the amidization process, potentially degrading the efficiency of the coupling chemistry. The work herein examines the efficiency of covalent protein immobilization in borate buffer (50 mM, pH 8.50) using the thiolate monolayer formed by the chemisorption of dithiobis (succinimidyl propionate) (DSP) on gold films. The structure and reactivity of these adlayers are assessed via infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), electrochemical reductive desorption, and contact angle measurements. The hydrolysis of the DSP-based monolayer is proposed to follow a reaction mechanism with an initial nucleation step, in contrast to a simple pseudo first-order reaction rate law for the entire reaction, indicating a strong dependence of the interfacial reaction on the packing and presence of defects in the adlayer. This interpretation is used in the subsequent analysis of IR-ERS kinetic plots which give a heterogeneous aminolysis rate constant, ka, that is over 3 orders of magnitude lower than that of the heterogeneous hydrolysis rate constant, kh. More importantly, a projection of these heterogeneous kinetic rates to protein immobilization suggests that under coupling conditions in which low protein concentrations and buffers of near physiological pH are used, proteins are more likely physically adsorbed rather than covalently linked. This result is paramount for biosensors that use NHS chemistry for protein immobilization due to effects that may arise from noncovalently linked proteins.

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Infrared spectra of the DSP-based adlayer after differentimmersiontimes in 50 mM borate buffer (pH 8.50).
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fig4: Infrared spectra of the DSP-based adlayer after differentimmersiontimes in 50 mM borate buffer (pH 8.50).

Mentions: The rate of the alkaline hydrolysisfor the NHS-activated ester monolayer was monitored as a functionof immersion time in borate buffer (pH 8.50, 50 mM) by IR-ERS. Asshown in Figure 4, the temporal evolution ofthe spectra is indicative of the progression in the hydrolytic lossof the NHS group. The νa(C=O) at 1748 cm–1, for example, decreases in strength by more than50% in less than 480 s; this feature is virtually undetectable after14 min. Other spectral features (e.g., N–C–Oband at 1074 cm–1 and the carboxylate vibrationband at 1265 cm–1) follow this trend but are tooweak in strength to be used for kinetic analysis.


Succinimidyl ester surface chemistry: implications of the competition between aminolysis and hydrolysis on covalent protein immobilization.

Lim CY, Owens NA, Wampler RD, Ying Y, Granger JH, Porter MD, Takahashi M, Shimazu K - Langmuir (2014)

Infrared spectra of the DSP-based adlayer after differentimmersiontimes in 50 mM borate buffer (pH 8.50).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4222659&req=5

fig4: Infrared spectra of the DSP-based adlayer after differentimmersiontimes in 50 mM borate buffer (pH 8.50).
Mentions: The rate of the alkaline hydrolysisfor the NHS-activated ester monolayer was monitored as a functionof immersion time in borate buffer (pH 8.50, 50 mM) by IR-ERS. Asshown in Figure 4, the temporal evolution ofthe spectra is indicative of the progression in the hydrolytic lossof the NHS group. The νa(C=O) at 1748 cm–1, for example, decreases in strength by more than50% in less than 480 s; this feature is virtually undetectable after14 min. Other spectral features (e.g., N–C–Oband at 1074 cm–1 and the carboxylate vibrationband at 1265 cm–1) follow this trend but are tooweak in strength to be used for kinetic analysis.

Bottom Line: The hydrolysis of the DSP-based monolayer is proposed to follow a reaction mechanism with an initial nucleation step, in contrast to a simple pseudo first-order reaction rate law for the entire reaction, indicating a strong dependence of the interfacial reaction on the packing and presence of defects in the adlayer.This interpretation is used in the subsequent analysis of IR-ERS kinetic plots which give a heterogeneous aminolysis rate constant, ka, that is over 3 orders of magnitude lower than that of the heterogeneous hydrolysis rate constant, kh.This result is paramount for biosensors that use NHS chemistry for protein immobilization due to effects that may arise from noncovalently linked proteins.

View Article: PubMed Central - PubMed

Affiliation: Departments of Chemical Engineering, ‡Chemistry, §Bioengineering, and ∥Pathology and the ⊥Nano Institute of Utah, University of Utah , Salt Lake City, Utah 84112, United States.

ABSTRACT
N-Hydroxysuccinimide (NHS) ester terminal groups are commonly used to covalently couple amine-containing biomolecules (e.g., proteins and peptides) to surfaces via amide linkages. This one-step aminolysis is often performed in buffered aqueous solutions near physiological pH (pH 6 to pH 9). Under these conditions, the hydrolysis of the ester group competes with the amidization process, potentially degrading the efficiency of the coupling chemistry. The work herein examines the efficiency of covalent protein immobilization in borate buffer (50 mM, pH 8.50) using the thiolate monolayer formed by the chemisorption of dithiobis (succinimidyl propionate) (DSP) on gold films. The structure and reactivity of these adlayers are assessed via infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), electrochemical reductive desorption, and contact angle measurements. The hydrolysis of the DSP-based monolayer is proposed to follow a reaction mechanism with an initial nucleation step, in contrast to a simple pseudo first-order reaction rate law for the entire reaction, indicating a strong dependence of the interfacial reaction on the packing and presence of defects in the adlayer. This interpretation is used in the subsequent analysis of IR-ERS kinetic plots which give a heterogeneous aminolysis rate constant, ka, that is over 3 orders of magnitude lower than that of the heterogeneous hydrolysis rate constant, kh. More importantly, a projection of these heterogeneous kinetic rates to protein immobilization suggests that under coupling conditions in which low protein concentrations and buffers of near physiological pH are used, proteins are more likely physically adsorbed rather than covalently linked. This result is paramount for biosensors that use NHS chemistry for protein immobilization due to effects that may arise from noncovalently linked proteins.

Show MeSH
Related in: MedlinePlus