Amorphous aggregates with a very wide size distribution play a central role in crystal nucleation.

There is mounting evidence that crystal nucleation from supersaturated solution involves the formation and reorganization of prenucleation clusters, contradicting classical nucleation theory. One of the key unresolved issues pertains to the origin, composition, and structure of these clusters. Here, a range of amino acids and peptides is investigated using light scattering, mass spectrometry, and in situ terahertz Raman spectroscopy, showing that the presence of amorphous aggregates is a general phenomenon in supersaturated solutions. Significantly, these aggregates are found on a vast range of length scales from dimers to 30-mers to the nanometre and even micrometre scale, implying a continuous distribution throughout this range. Larger amorphous aggregates are sites of spontaneous crystal nucleation and act as intermediates for laser-induced crystal nucleation. These results are shown to be consistent with a nonclassical nucleation model in which barrierless (homogeneous) nucleation of amorphous aggregates is followed by the nucleation of crystals from solute-enriched aggregates. This provides a novel perspective on crystal nucleation and the role of nonclassical pathways.

Ion Mobility Mass Spectrometry Unveils Global Protein Conformations in Response to Conditions that Promote and Reverse Liquid-Liquid Phase Separation.

Liquid-liquid phase separation (LLPS) is a process by which biomacromolecules, particularly proteins, condense into a dense phase that resembles liquid droplets. Dysregulation of LLPS is implicated in disease, yet the relationship between protein conformational changes and LLPS remains difficult to discern. This is due to the high flexibility and disordered nature of many proteins that phase separate under physiological conditions and their tendency to oligomerize. Here, we demonstrate that ion mobility mass spectrometry (IM-MS) overcomes these limitations. We used IM-MS to investigate the conformational states of full-length ubiquilin-2 (UBQLN2) protein, LLPS of which is driven by high-salt concentration and reversed by noncovalent interactions with ubiquitin (Ub). IM-MS revealed that UBQLN2 exists as a mixture of monomers and dimers and that increasing salt concentration causes the UBQLN2 dimers to undergo a subtle shift toward extended conformations. UBQLN2 binds to Ub in 2:1 and 2:2 UBQLN2/Ub complexes, which have compact geometries compared to free UBQLN2 dimers. Together, these results suggest that extended conformations of UBQLN2 are correlated with UBQLN2's ability to phase separate. Overall, delineating protein conformations that are implicit in LLPS will greatly increase understanding of the phase separation process, both in normal cell physiology and disease states.

Demonstrating efficacy of rural land management actions to improve water quality - How can we quantify what actions have been done?

Despite several decades of encouraging land management actions to improve water quality on rural land, we are still struggling to accurately quantify what management actions have been implemented, where these actions have been used and the intensity of implementation. This is largely because standardised approaches to recording and reporting of land management actions have not been established, resulting in a lack of robust information that can be used to determine the effectiveness and longevity of these actions at a catchment or larger scale. Better information on the effectiveness of different land management actions will provide land managers with more certainty that their investments in land management actions will make a difference. We reviewed a total of 91 global publications and proceedings between 1989 and 2019 which assessed the complexities related to recording and reporting sustainable land use actions with a focus on freshwater ecosystems in rural areas in the developed world. We then summarised these complexities (i.e., temporal and spatial lag-effects, confidentiality issues, lack of data robustness) and mined the literature about methodologies on how actions can be measured, how to address the challenges with doing this and recommended a suite of indicators of land management actions that could be standardised and widely used to improve water quality. Our review of literature identified numerous sources describing land management actions, but little information on standardised indicators of location, scale and intensity of the most common actions. Some common actions are measured using a wide variety of incompatible approaches (e.g., riparian management is often indicated by length of fencing, width of vegetated buffer strips, proportion of the catchment with stock exclusion), whereas other indicators of land management action are at such a high level (e.g., costs) that they do not provide information on the actions used. The scale/intensity of land management efforts is often not reported spatially with information typically restricted to small scales such as single point location information, making it difficult, if not impossible to determine the scale of actions within a catchment relative to a given water quality monitoring site.

Perspectives on analyses of nucleic acid constituents: the basis of genomics.

The recent mapping of the human genome was a tremendous achievement made possible to a large degree by the development of analytical methods for sequencing purine and pyrimidine bases in nucleic acids. In the last 3 decades, the number of analyses of nucleic acids and their constituents by HPLC and capillary electrophoresis (CE) has exploded. These techniques have been used not only for genomics, but also for the determination of free nucleotides, nucleosides and their bases in body fluids and tissues. Although a large number of HPLC and CE papers have been published on nucleic acid constituent applications, relatively little has been written on the mechanisms of the separations. However, to optimize analytical conditions knowledgeably and rapidly, it is important to know why and how these separations occur and the factors that affect them. The HPLC methods for the analysis of nucleic acid constituents and the information available on some of the mechanisms of separation of nucleotides, nucleosides and their bases, as well as the analysis of these compounds by CE and the factors that affect these separations are discussed.

Capillary electrophoretic separation by double-strand polyaniline-coate capillaries of the advanced glycation endproducts formed from N-alpha-acetyl-L-lysine with reducing sugars.

Capillary electrophoresis using a capillary coated with a double-strand coating of polyaniline:poly(methyacrylate-co-acrylic acid) (PAN:P[MA-AAI) was used to separate advanced glycation endproducts (AGEs) formed at 37 degrees C from model systems containing either glucose (Glc), fructose (Fru), or glyceraldehyde (GA) and N-alpha-acetyl-L-lysine (NALys). The presence of the P(MA-AA) as a second strand in the polymer allows the maintenance of the conductive state of the PAN at a wide pH range. Effects of buffer pH and coating concentration on the electroosmotic flow (EOF) were investigated. More AGE species can be detected for the GA/NALys mixtures using this coated capillary than upon an uncoated capillary. The coating procedure is simple and the stability of the coated capillary is good.

Enhanced analysis of purine and pyrimidine bases by the use of double-strand polyaniline coatings in micellar electrokinetic capillary chromatography.

A double-strand polymeric complex, which suppresses electroosmotic flow relative to fused-silica, is described. The polymeric complex contains a strand polyaniline (PAN) with the second strand containing polyacrylic acid (PAA) and methacrylate (MA) groups. The complex is referred to as PAN:P(AAMA). This polymeric complex has pH-controlled electroactive and hydrophobic characteristics and can be easily coated onto fused-silica. Enhanced separations of theophylline, theobromine, caffeine and adenine, thymine, uracil and cytosine were obtained by the use of the coated capillary in the micellar electrokinetic capillary electrophoresis (MEKC) system. The purine and pyrimdine bases were separated on the coated capillary with a 20 mM, pH 7 phosphate buffer which contains 0.05 M sodium dodecyl sulfate (SDS) as an additive.