Hannu Salo

Bile acid alkylamide derivatives as low molecular weight organogelators: Systematic gelation studies and qualitative structural analysis of the systems

A series of amino- and hydroxyalkyl amides of bile acids have been synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), (1)H and (13)C nuclear magnetic resonance spectroscopy (NMR), as well as electrospray ionization mass spectrometry (ESI-MS) measurements. The ability of the synthesized molecules to promote gel formation was systematically investigated. Out of 396 combinations formed by 11 compounds and 36 different solvents, 22 gel-containing systems were obtained with 1% (w/v) gelator concentration. Apart from one exception, the gelator compounds were lithocholic acid derivatives. This challenges the general trend of bile acid-based physical gelators, according to which the gelation ability of lithocholic acid derivatives is poor. A correlation between the values of Kamlet-Taft parameters and solvent preferences for gelators was observed. The morphologies of the solid and gel structures studied with scanning electron microscopy (SEM) showed variability from fibers to spherical microscale aggregates, the latter of which are unique among bile acid-based organogels. The gels exhibited more complex behavior than was previously established with bile acid derivatives, judging by the microscale diversity present in gelating and non-gelating systems and the tendency for polymorphism. This study underlines the importance of both the molecular and colloidal scale aspects of the gelation phenomenon.

Bile acid–amino acid ester conjugates: gelation, structural properties, and thermoreversible solid to solid phase transition

Design, synthesis, and gelation properties of three novel biocompatible bile acid–L-methionine methyl ester conjugates are presented. Two of the conjugates have been shown to undergo self-assembly leading to organogelation in certain aromatic solvents. The properties of these gels have been investigated by conventional methods typical for molecular gel studies along with 13C CPMAS NMR spectroscopic studies of the native gel. In addition, properties in solid and solution states for all three compounds have been investigated, and single crystal X-ray structures of all compounds determined. Furthermore, powder X-ray diffraction studies have revealed that compound 1 undergoes a dynamic and reversible conformational change in the solid state when cooling from ambient temperature to −150 °C. The powder X-ray diffraction data of the room-temperature conformer has been utilized to unambiguously determine the structure at room temperature.

Bile acid-cysteamine conjugates: structural properties, gelation, and toxicity evaluation.

Design, synthesis, and characterization of six novel bile acid-cysteamine conjugates together with investigation of their structural studies, gelation properties, and preliminary toxicity evaluation, are reported. Solid state properties of selected compounds were studied by means of X-ray diffraction and (13)C CPMAS NMR spectroscopy. N-(2-thioethyl)-3α,7α,12α-trihydroxy-5β-cholan-24-amide was shown to exhibit (pseudo)polymorphism, and a single crystal structure of its non-stoichiometric hydrate is reported herein. Cholyl and dehydrocholyl derivatives bearing three functionalities in their steroidal backbone were shown to undergo self-assembly leading to gelation in certain organic solvents. Preliminary morphology studies of the formed gels by scanning electron microscopy (SEM) were performed. The standard model mouse fibroblast cell line together with the MTT and NR tests were utilized for evaluating the toxicity of the prepared compounds. Lithocholyl, ursodeoxycholyl, and dehydrocholyl derivatives turned out to be relatively non-toxic in the conditions studied.

The Adaptation of Professional Fishing to Diminished Vendace Stocks: The Case of Finnish Inland Waters

Abstract The large number of lakes covering 10% of Finlands surface area provide an opportunity for both full-time and part-time professional fishing. However, the development of the fishing industry is hindered by unpredictable fluctuations in fish stocks, by the elaborate hierarchy of the fisheries system, as well as by certain features of Finnish professional fishing, such as the small size of fishing enterprises, the scattered pattern of production, and long transportation distances to the core demand areas. According to Finnish catch statistics, the stock of vendace Coregonus albula has clearly diminished since the mid 1980s. Our results show that full-time professional fishermen differ from part-time professional fishermen in their adaptation to diminished fish stocks: they increase their fishing efforts, they try to extend their fishing grounds, and they switch to or supplement with a new species. Moreover, their desire to develop their fishing is stronger than that of part-time professional fishe...

3α,3′α-Bis(n-acetoxyphenylcarboxy)-5β-cholan-24-oic acid ethane-1,2-diol diesters (n = 2-4):13C NMR chemical shifts, variable-temperature and NOE1H NMR measurements and MO calculations of novel bile acid-based dimers

Three novel bile acid‐based molecular dimers, 3α,3′α‐bis(n‐acetoxyphenylcarboxy)‐5β‐cholan‐24‐oic acid ethane‐1,2‐diol diesters (n = 2–4), 1–3, were synthesized from lithocholic acid (3α‐hydroxy‐5β‐cholan‐24‐oic acid) ethane‐1,2‐diol diester and isomeric n‐acetoxybenzoyl chlorides (n = 2–4). Their cleft type conformational preferences were suggested theoretically by PM3 molecular orbital calculations. Molecular weights determined by the matrix‐assisted laser desorption/ionization time‐of‐flight technique and 13C NMR chemical shifts of the 1–3 are also presented. Copyright

Self-assembly properties of bile acid derivatives of l-cysteine, l-valine and l-serine alkyl esters

Comprehensive self-assembly studies for nine bile acid amides of amino acid esters are reported. The number of the hydroxyl groups attached to the steroidal skeleton and the character of the amino acid ester moiety were used as variables when examining the self-assembly properties of the compounds. Two of the compounds were shown to undergo self-assembly leading to organogelation. In addition, preliminary self-assembly studies in aqueous mixtures of polar organic solvents were conducted. Microscopic methods (optical microscopy and scanning electron microscopy) were utilised in order to gain a deeper insight into the self-assembled structures. Furthermore, single-crystal X-ray structures for three of the compounds were solved.

Stimuli-responsive bile acid-based metallogels forming in aqueous media

The synthesis and gelation properties of a picolinic acid conjugated bile acid derivative in the presence of metal salts along with the stimuli-responsiveness of the systems are reported. The gels are formed in the presence of Cu(2+) ions in the solvent systems composed of 30-50% of organic solvent (MeOH, acetonitrile, or acetone) in water. The gels respond to various stimuli: they can be formed upon sonication or shaking, and their gel-sol transformation can be triggered by a variety of chemical species. NMR, MS, and SEM techniques are exploited in order to gain a deeper insight on the self-assembled systems.

13C NMR spectral assignments of 3α,3′α‐bis(arylcarboxy)‐5β‐cholan‐24‐oic acid ethane‐1,2‐diol diesters: new lithocholic acid‐based molecular clefts

3α,3′α‐Bis(arylcarboxy)‐5β‐cholan‐24‐oic acid ethane‐1,2‐diol diesters (1–3) were synthesized by the reaction of an aroyl chloride (aroyl=2,6‐dichlorobenzoyl, 2‐naphthoyl and 1‐pyrenoyl) with lithocholic acid (3α‐hydroxy‐5β‐cholan‐24‐oic acid) ethane‐1,2‐diol diester. The 13C NMR chemical shift assignments of the formed molecular clefts 1–3, pyrene‐1‐carboxylic acid methyl ester (4) (used as model compound) and 1‐pyrenoyl chloride (5) are based on literature data and 13C DEPT‐135, 1H,13C HMQC and 1H,13C HMBC experiments. The molecular weights of 1–3 were determined by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Copyright

Gelation Behavior of 5-Chloro-8-hydroxyquinoline, an Antituberculosis Agent in Aqueous Alcohol Solutions

It was shown that 5-chloro-8-hydroxyquinoline, an antituberculosis agent, gels aqueous alcohol solutions efficiently. Thermal stability and gel-to-sol transition temperature of 1% gel in CD3OD/D2O (2:1) was studied by 1H-NMR. Fibrous structures of four xerogels have been characterized by scanning electron microscope.

Biocompatible Hydrogelators Based on Bile Acid Ethyl Amides

Four novel bile acid ethyl amides were synthetized using a well-known method. All the four compounds were characterized by IR, SEM, and X-ray crystal analyses. In addition, the cytotoxicity of the compounds was tested. Two of the prepared compounds formed organogels. Lithocholic acid derivative 1 formed hydrogels as 1% and 2% (w/v) in four different aqueous solutions. This is very intriguing regarding possible uses in biomedicine.