Serum albumin, a protein naturally abundant in blood plasma, shows remarkable ligand binding properties of numerous endogenous and exogenous compounds. Most of serum albumin binding sites are able to interact with more than one class of ligands. Determining the protein-ligand interactions among mammalian serum albumins is essential for understanding the complexity of this transporter. We present three crystal structures of serum albumins in complexes with naproxen (NPS): bovine (BSA-NPS), equine (ESA-NPS), and leporine (LSA-NPS) determined to 2.58 Å (C2), 2.42 Å (P61), and 2.73 Å (P2₁2₁2₁) resolutions, respectively. A comparison of the structurally investigated complexes with the analogous complex of human serum albumin (HSA-NPS) revealed surprising differences in the number and distribution of naproxen binding sites. Bovine and leporine serum albumins possess three NPS binding sites, but ESA has only two. All three complexes of albumins studied here have two common naproxen locations, but BSA and LSA differ in the third NPS binding site. None of these binding sites coincides with the naproxen location in the HSA-NPS complex, which was obtained in the presence of other ligands besides naproxen. Even small differences in sequences of serum albumins from various species, especially in the area of the binding pockets, influence the affinity and the binding mode of naproxen to this transport protein.

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Serum albumin, the most abundant transport protein of mammalian blood, interacts with various nonsteroidal anti‐inflammatory drugs (NSAIDs) affecting their disposition, metabolism, and excretion. A big group of chiral NSAIDs transported by albumin, profens, is created by derivatives of 2‐arylpropionic acid. The chiral center in the structures of profens is adjacent to the carboxylate moiety and often determines different pharmacological properties of profen enantiomers. This study describes crystal structures of two albumins, isolated from equine and leporine serum, in complexes with three profens: ibuprofen, ketoprofen, and suprofen. Based on three‐dimensional structures, the stereoselectivity of albumin is discussed and referred to the previously published albumin complexes with drugs. Drug Site 2 (DS2) of albumin, the bulky hydrophobic pocket of subdomain IIIA with a patch of polar residues, preferentially binds (S)‐enantiomers of all investigated profens. Almost identical binding mode of all these drugs clearly indicates the stereoselectivity of DS2 towards (S)‐profens in different albumin species. Also, the affinity studies show that DS2 is the major site that presents high affinity towards investigated drugs. Additionally, crystallographic data reveal the secondary binding sites of ketoprofen in leporine serum albumin and ibuprofen in equine serum albumin, both overlapping with previously identified naproxen binding sites: the cleft formed between subdomains IIIA and IIIB close to the fatty acid binding site 5 and the niche created between subdomains IIA and IIIA, called fatty acid site 6.

Serum albumin (SA) is the most abundant protein in plasma and is the main transporter of molecules in the circulatory system of all vertebrates, with applications in medicine, the pharmaceutical industry and molecular biology. It is known that albumins from different organisms vary in sequence; thus, it is important to know the impact of the amino-acid sequence on the three-dimensional structure and ligand-binding properties. Here, crystal structures of ovine (OSA) and caprine (CSA) serum albumins, isolated from sheep and goat blood, are described, as well those of their complexes with 3,5-diiodosalicylic acid (DIS): OSA-DIS (2.20 Å resolution) and CSA-DIS (1.78 Å resolution). The ligand-free OSA structure was determined in the trigonal space group P321 at 2.30 Å resolution, while that of CSA in the orthorhombic space group P222 was determined at 1.94 Å resolution. Both albumins are also capable of crystallizing in the triclinic space group P1, giving isostructural crystals that diffract to around 2.5 Å resolution. A comparison of OSA and CSA with the closely related bovine serum albumin (BSA) shows both similarities and differences in the distribution of DIS binding sites. The investigated serum albumins from domesticated ruminants in their complexes with DIS are also compared with the analogous structures of equine and human serum albumins (ESA-DIS and HSA-DIS). Surprisingly, despite 98% sequence similarity, OSA binds only two molecules of DIS, whereas CSA binds six molecules of this ligand. Moreover, the binding of DIS to OSA and CSA introduced changes in the overall architecture of the proteins, causing not only different conformations of the amino-acid side chains in the binding pockets, but also a significant shift of the whole helices, changing the volume of the binding cavities.

Introduction: Calculating accurate blood volume to process is a critical practice in apheresis planning; therefore, researchers try to develop dedicated prediction models. In this analysis, we have attempted to compare three algorithms for two different apheresis collection protocols.Methods: In a retrospective study, we have analyzed 137 apheresis procedures performed on 100 autologous patients. Apheresis procedures were performed with the Spectra Optia apheresis device with two protocols: mononuclear cell collection (MNC) and continuous mononuclear cell collection (cMNC). Three algorithms: a model based on mean collection efficiency (CE2), a linear regression model, and a power regression model were validated by plotting collected CD34 + cell dose versus predicted CD34 + cell dose.Results: All models showed high predictability for MNC procedure, a high correlation of predicted CD34 + yield and actual CD34 + yield (R 2 =0.9547; 0.9487; 0.9474 for CE2-based model, linear and power regression model, respectively). In contrast, alteration between models for the cMNC procedure was greater (R 2 =0.8049, 0.7970, and 0.8169) with a higher number of overpredictions. Further analysis revealed that for low CD34 + precounts blood volume to process, calculated with the three models, differ significantly up to fivefold times.Conclusions: Utilizing regression models may lead to calculation errors, which can affect undercollection, repetition of apheresis, or even mobilization failure. Contrary to regression models, the model based on mean CE2 gave the most accurate prediction both for MNC and cMNC procedures. Although new prediction algorithms are created, this simple formula remains a reliable tool that promotes careful planning of apheresis, thus improving patient safety.