Surface Chemistry Studies on the Formation of Mixed Stearic Acid/Phenylalanine Dehydrogenase Langmuir and Langmuir-Blodgett Films

Author(s)

Cruz Gomes da Silva, Rafael Leonardo ^[1] ; Sharma, Shiv K. ^[2] ; Paudyal, Suraj ^[2] ; Mintz, Keenan J. ^[2] ; Leblanc, Roger M. ^[2] ; Caseli, Luciano ^[1]

Affiliation

^[1] Univ Fed Sao Paulo, Dept Chem, BR-09920540 Diadema, SP - Brazil

^[2] Univ Miami, Dept Chem, Coral Gables, FL 33146 - USA

• Document type: Journal article
• Source: Langmuir; v. 37, n. 25, p. 7771-7779, JUN 29 2021.
• Web of Science Citations: 0

Abstract

This work investigates the physicochemical properties of mixed stearic acid (HSt)/phenylalanine dehydrogenase enzyme (PheDH) Langmuir films and their immobilization onto solid supports as Langmuir-Blodgett (LB) films. PheDH from the aqueous subphase enters the surfactant matrix up to an exclusion surface pressure of 25.3 mN/m, leading to the formation of stable and highly condensed mixed Langmuir monolayers. Hydrophobic interactions between the enzyme and HSt nonpolar groups tuned the secondary structure of PheDH, evidenced by the presence of beta-sheet structures as demonstrated by infrared and circular dichroism spectra. The floating monolayers were successfully transferred to solid quartz supports, yielding Y-type LB films, and then characterized employing fluorescence, circular dichroism, and microscopic techniques, which indicated that PheDH was co-immobilized with HSt proportionally to the number of transferred layers. The enzyme fluidized the HSt monolayers, reducing their maximum dipoles when condensed to their maximum, and disorganized the alkyl chains of the fatty acid, as detected with infrared spectroscopy. The stability of the mixed floating monolayers enabled their transfer to solid supports as LB films, which is important for producing optical and electrochemical sensors for phenylalanine whose molecular architecture can be controlled with precision. (AU)

• FAPESP's process: 19/01797-6 - Langmuir and Langmuir-Blodgett films of lipids containing phenylalanine dehydrogenase for phenylalanine biosensors
• Grantee: Rafael Leonardo Cruz Gomes da Silva
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• FAPESP's process: 18/22214-6 - Towards a convergence of technologies: from sensing and biosensing to information visualization and machine learning for data analysis in clinical diagnosis
• Grantee: Osvaldo Novais de Oliveira Junior
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 18/00291-9 - Langmuir and Langmuir-Blodgett films of lipids containing phenylalanine dehydrogenase for sensors of phenylalanine
• Grantee: Rafael Leonardo Cruz Gomes da Silva
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 19/03239-0 - Nanostructured interfaces for the investigation of bioactive substances in cell membrane models and for the construction of optoelectronic devices
• Grantee: Luciano Caseli
• Support Opportunities: Regular Research Grants