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1. Conformation and Aggregation of Human Serum Albumin in the Presence of Green Tea Polyphenol (EGCg) and/or Palmitic Acid

   Sun, Xiaowei; Ferguson, Haley N.; Hagerman, Ann E. (November 2020, Biomolecules)

   Polyphenols such as epigallocatechin gallate (EGCg) may have roles in preventing some chronic diseases when they are ingested as components of plant-based foods and beverages. Human serum albumin (HSA) is a multi-domain protein that binds various ligands and aids in their transport, distribution, and metabolism in the circulatory system. In the present study, the HSA-EGCg interaction in the absence or presence of fatty acid has been investigated. Förster resonance energy transfer (FRET) was used to determine inter- and intra-domain distances in the protein with and without EGCg and palmitic acid (PA). By labeling Cys-34 with 7-(diethyl amino)-4-methylcoumarin 3-maleimide (CPM), the distance between Trp-214 at domain IIA and CPM-Cys-34 at domain IA could be established. A small amount of PA decreased the distance, while a large amount increased the distance up to 5.4 Å. EGCg increased the inter-domain distance in HSA and HSA-PA up to 2.8 and 7.6 Å, respectively. We concluded that PA affects protein conformation more significantly compared to EGCg. Circular dichroism (CD) established that EGCg affects protein secondary structure more significantly than PA. PA had little effect on the α-helix content of HSA, while EGCg decreased the α-helix content in a dose-dependent fashion. Moreover, EGCg decreased α-helix content in HSA and HSA-PA to the same level. Dynamic light scattering (DLS) data revealed that both PA and EGCg increased HSA aggregation. EGCg increased HSA aggregation more significantly and promoted formation of aggregates that were more heterogenous. Any of these effects could impact the ability of serum albumin to transport and stabilize ligands including EGCg and other polyphenols. 

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2. Electro-hydrodynamic extraction of DNA from mixtures of DNA and bovine serum albumin

   https://doi.org/10.1039/D0AN00961J  

   Valley, Benjamin E.; Crowell, Anne D.; Butler, Jason E.; Ladd, Anthony J. (August 2020, The Analyst)

   null (Ed.)

   We report separation of genomic DNA (48 kbp) from bovine serum albumin (BSA) by the electro-hydrodynamic coupling between a pressure-driven flow and a parallel electric field. Electro-hydrodynamic extraction exploits this coupling to trap DNA molecules at the entrance of a microfluidic contraction channel, while allowing proteins and salts to be flushed from the device. Samples (10 μL) containing λ-DNA (1 ng) and BSA (0.3 mg) were injected directly into the device and convected to the contraction channel entrance by a flowing buffer solution. The DNA remains trapped in this region essentially indefinitely, while proteins and salts are eluted. The effectiveness of the concept has been assessed by fluorescence measurements of DNA and BSA concentrations. Electro-hydrodynamic extraction in a single-stage device was found to enhance the concentration of DNA 40-fold, while reducing the BSA concentration by four orders of magnitude. The relative concentrations of DNA to BSA at the contraction channel entrance can be as large as 1.5 : 1, corresponding to an A260/280 ratio of 1.9. The maximum yield of DNA from a salt-free solution is 50%, while salted (150 mM) solutions have a lower yield (38%). 

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3. Metal−Organic Polyhedron with Four Fe(III) Centers Producing Enhanced T1 Magnetic Resonance Imaging Contrast in Tumors

   https://doi.org/doi.org/10.1021/acs.inorgchem.1c03660  

   Gregory E. Sokolow, Matthew R. (January 2022, Inorganic chemistry)

   ABSTRACT: A metal organic polyhedron (MOP) with four paramagnetic Fe(III) centers was studied as a magnetic reso-nance imaging (MRI) probe. The MOP was characterized in solution by using EPR and UV-vis spectroscopies, FT-ICR mass spectrometry, and in the solid state with single crystal x-ray diffraction. Water proton T1 relaxation properties were examined in solution and showed significant enhancement in the presence of human serum albumin (HSA). The r1 relaxivities in the absence and presence of HSA were 8.7 mM-1s-1 and 21 mM-1s-1, respectively, per molecule (2.2 and 5.3 per Fe) at 4.7 T, 37 °C. In vivo studies of the iron MOP show strong contrast enhancement of blood pool even at a low dose of 0.025 mmol/kg with prolonged residence in vasculature and clearance through the intestinal tract of mice. The MOP binds strongly to serum albumin and shows comparable accumulation in a murine tumor model as a covalently linked Gd-HSA contrast agent. 

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4. Hydrolysis of chemically distinct sites of human serum albumin by polyoxometalate: A hybrid QM/MM (ONIOM) study

   https://doi.org/10.1002/jcc.25528  

   Jayasinghe‐Arachchige, Vindi M.; Hu, Qiaoyu; Sharma, Gaurav; Paul, Thomas J.; Lundberg, Marcus; Quinonero, David; Parac‐Vogt, Tatjana N.; Prabhakar, Rajeev (September 2018, Journal of Computational Chemistry)

   In this study, mechanisms of hydrolysis of all four chemically diverse cleavage sites of human serum albumin (HSA) by [Zr(OH)(PW₁₁O₃₉)]⁴⁻(ZrK) have been investigated using the hybrid two‐layer QM/MM (ONIOM) method. These reactions have been proposed to occur through the following two mechanisms: internal attack (IA) and water assisted (WA). In both mechanisms, the cleavage of the peptide bond in the Cys392‐Glu393 site of HSA is predicted to occur in the rate‐limiting step of the mechanism. With the barrier of 27.5 kcal/mol for the hydrolysis of this site, the IA mechanism is found to be energetically more favorable than the WA mechanism (barrier = 31.6 kcal/mol). The energetics for the IA mechanism are in line with the experimentally measured values for the cleavage of a wide range of dipeptides. These calculations also suggest an energetic preference (Cys392‐Glu393, Ala257‐Asp258, Lys313‐Asp314, and Arg114‐Leu115) for the hydrolysis of all four sites of HSA. © 2018 Wiley Periodicals, Inc. 

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5. Secured delivery of basic fibroblast growth factor using human serum albumin-based protein nanoparticles for enhanced wound healing and regeneration

   https://doi.org/10.1186/s12951-023-02053-4  

   Son, Boram; Kim, Minju; Won, Hyosub; Jung, Ara; Kim, Jihyun; Koo, Yonghoe; Lee, Na Kyeong; Baek, Seung-Ho; Han, Uiyoung; Park, Chun Gwon; et al (December 2023, Journal of Nanobiotechnology)

   Abstract BackgroundBasic fibroblast growth factor (bFGF) is one of the critical components accelerating angiogenesis and tissue regeneration by promoting the migration of dermal fibroblasts and endothelial cells associated with matrix formation and remodeling in wound healing process. However, clinical applications of bFGF are substantially limited by its unstable nature due to rapid decomposition under physiological microenvironment. ResultsIn this study, we present the bFGF-loaded human serum albumin nanoparticles (HSA-bFGF NPs) as a means of enhanced stability and sustained release platform during tissue regeneration. Spherical shape of the HSA-bFGF NPs with uniform size distribution (polydispersity index < 0.2) is obtainedviaa simple desolvation and crosslinking process. The HSA-bFGF NPs securely load and release the intact soluble bFGF proteins, thereby significantly enhancing the proliferation and migration activity of human dermal fibroblasts. Myofibroblast-related genes and proteins were also significantly down-regulated, indicating decrease in risk of scar formation. Furthermore, wound healing is accelerated while achieving a highly organized extracellular matrix and enhanced angiogenesis in vivo. ConclusionConsequently, the HSA-bFGF NPs are suggested not only as a delivery vehicle but also as a protein stabilizer for effective wound healing and tissue regeneration. 

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