The biosynthesis of 'unusual' fatty acids with structures that deviate from the common C and C fatty acids has evolved numerous times in the plant kingdom. Characterization of unusual fatty acid biosynthesis has enabled increased understanding of enzyme substrate properties, metabolic plasticity and oil functionality. Here, we report the identification of a novel pathway for hydroxy fatty acid biosynthesis based on the serendipitous discovery of two C fatty acids containing hydroxyl groups at the 7 and 18 carbon atoms as major components of the seed oil of Orychophragmus violaceus, a China-native Brassicaceae. Biochemical and genetic evidence are presented for premature or 'discontinuous' elongation of a 3-OH intermediate by a divergent 3-ketoacyl-CoA (coenzyme A) synthase during a chain extension cycle as the origin of the 7-OH group of the dihydroxy fatty acids. Tribology studies revealed superior high-temperature lubricant properties for O. violaceus seed oil compared to castor oil, a high-performance vegetable oil lubricant. These findings provide a direct pathway for designing a new class of environmentally friendly lubricants and unveil the potential of O. violaceus as a new industrial oilseed crop.

Design of environmentally friendly lubricants derived from renewable resources is highly desirable for many practical applications. Here, Orychophragmus violaceus (Ov) seed oil is found to have superior lubrication properties, and this is based on the unusual structural features of the major lipid species—triacylglycerol (TAG) estolides. Ov TAG estolides contain two non-hydroxylated, glycerol-bound fatty acids (FAs) and one dihydroxylated FA with an estolide branch. Estolide branch chains vary in composition and length, leading to their thermal stability and functional properties. Using this concept, nature-guided estolides of castor oil were synthesized. As predicted, they showed improved lubrication properties similar to Ov seed oil. Our results demonstrate a structure-based design of novel lubricants inspired by natural materials.

The artificial joints, for example, knee and hip implants, are widely used for the treatment of degenerative joint diseases and trauma. The current most common material choice for clinically used implants is the combination of polymer-on-metal structures. Unfortunately, these joints often suffer from high friction and wear, leading to associated inflammation and infection and ultimate failure of the artificial joints. Here, we propose an alternative solution to this tribologically induced failure of the joint materials. We demonstrate that the friction and wear behavior of ultrahigh-molecular-weight polyethylene (UHMWPE) and titanium tribopair, used to mimic the artificial joint interface, can be improved by introducing nanodiamond (ND) particles in the sliding contact. Characterization of the wear track using energy-dispersive spectroscopy and Raman spectroscopy revealed that the tribofilm formed from embedded NDs during sliding significantly suppressed the wear of the UHMWPE surface. In addition to the improved lubrication characteristics, NDs exhibit high biocompatibility with the bone cells and promising antibacterial properties against Staphylococcus aureus, the most common strain associated with artificial joint infection. These results indicate that NDs can be used as a promising nontoxic human-body lubricant with antiwear and antibacterial features, thus demonstrating their great potential to treat artificial joint complications through intra-articular injection.

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Here, we report the high-temperature superlubricity phenomenon accomplished in coatings produced by burnishing powders of antimony trioxide (Sb2O3) and magnesium silicate hydroxide coated with carbon (MSH/C) onto the nickel superalloy substrate. The tribological analysis performed in an open-air experimental setup revealed that with the increase of testing temperature, the coefficient of friction (COF) of the coating gradually decreases, finally reaching the superlubricity regime (the COF of 0.008) at 300°C. The analysis of worn surfaces using in-situ Raman spectroscopy suggested the synergistic effect of the inner Sb2O3 adhesion layer and the top MSH/C layer, which do not only isolate the substrate from the direct exposure to sliding but also protect it from oxidation. The cross-sectional transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results indicated the tribochemically-activated formation of an amorphous carbon layer on the surface of the coating during sliding. Formation of the film enables the high-temperature macroscale superlubricity behavior of the material system.