Oligonucleotide chemistry has been developed greatly over the past three decades, with many advances in increasing nuclease resistance, enhancing duplex stability and assisting with cellular uptake. Locked nucleic acid (LNA) is a structurally rigid modification that increases the binding affinity of a modified-oligonucleotide. In contrast, unlocked nucleic acid (UNA) is a highly flexible modification, which can be used to modulate duplex characteristics. In this tutorial review, we will compare the synthetic routes to both of these modifications, contrast the structural features, examine the hybridization properties of LNA and UNA modified duplexes, and discuss how they have been applied within biotechnology and drug research. LNA has found widespread use in antisense oligonucleotide technology, where it can stabilize interactions with target RNA and protect from cellular nucleases. The newly emerging field of siRNAs has made use of LNA and, recently, also UNA. These modifications are able to increase double-stranded RNA stability in serum and decrease off-target effects seen with conventional siRNAs. LNA and UNA are also emerging as versatile modifications for aptamers. Their application to known aptamer structures has opened up the possibility of future selection of LNA-modified aptamers. Each of these oligonucleotide technologies has the potential to become a new type of therapy to treat a wide variety of diseases, and LNA and UNA will no doubt play a part in future developments of therapeutic and diagnostic oligonucleotides.
Background A decline in hospitalization for cardiovascular events and catheter laboratory activation was reported for the United States and Italy during the initial stage of the Covid-19 pandemic of 2020. We report on the deployment of emergency services for cardiovascular events in a defined region in western Germany during the government-imposed lock-down period. Methods We examined 5799 consecutive patients who were treated by emergency services for cardiovascular events during the Covid-19 pandemic (January 1 to April 30, 2020), and compared those to the corresponding time frame in 2019. Examining the emergency physicians’ records provided by nine locations in the area, we found a 20% overall decline in cardiovascular admissions. Results The greatest reduction could be seen immediately following the government-imposed social restrictions. This reduction was mainly driven by a reduction in discretionary admissions for dizziness/syncope (-53%), heart failure (-38%), exacerbated COPD (-28%) and unstable angina (-23%), while unavoidable admissions for ST-elevation myocardial infarction (STEMI), cardiopulmonary resuscitation (CPR) and stroke were unchanged. There was a greater decline in emergency admissions for patients ≥60 years. There was also a greater reduction in emergency admissions for those living in urban areas compared to suburban areas. Conclusions During the Covid-19 pandemic, a significant decline in hospitalization for cardiovascular events was observed during the government-enforced shutdown in a predefined area in western Germany. This reduction in admissions was mainly driven by “discretionary” cardiovascular events (unstable angina, heart failure, exacerbated COPD and dizziness/syncope), but events in which admission was unavoidable (CPR, STEMI and stroke) did not change.
Novel pyrene-perylene α-L-LNA FRET pairs described herein effectively detect assembly of 2- and 3-way branched DNA nanostructures prepared by postsynthetic microwave-assisted CuAAC click chemistry. The fluorescent signalling of assembly by internally positioned FRET pairs is achieved with low to no fluorescence background signal, remarkably low limit of target detection values and stabilization of the resulting nanostructures.
Herein we introduce a novel fluorescent LNA/DNA machine, a nanocrawler, which reversibly moves along a directionally polar complementary road controlled by affinity-enhancing locked nucleic acid (LNA) monomers and additional regulatory strands. Polyaromatic hydrocarbon (PAH) dyes attached to 2'-amino-LNA monomers are incorporated at four stations of the system, enabling simple detection of the position of the nanocrawler via a step-specific color signal. The sensing is provided by highly sensitive, chemically stable, and photostable PAH LNA interstrand communication systems, including pyrene excimer formation and pyrene-perylene interstrand Förster resonance energy transfer. We furthermore demonstrate that the nanocrawler selectively and reversibly moves along the road, followed by a bright and consistent fluorescence response for up to 10 cycles without any loss of signal.
The cancer chemotherapeutic agent cis-diamminedichloroplatinum(II) or cisplatin reacts primarily with guanines in DNA to form 1,2-Pt-GG and 1,3-Pt-GNG intrastrand cross-links, and to a lesser extent, G-G interstrand cross-links. Recent NMR evidence has suggested that cisplatin can also form a coordination complex with the phosphodiester internucleotide linkage of DNA. We have examined the effects of the phosphodiester backbone on the reactions of cisplatin with oligodeoxyribonucleotides that lack or contain a -GTG-sequence. Cisplatin forms a stable adduct with TpT that can be isolated by reversed phase HPLC. The cis-Pt-TpT adduct contains a single Pt, as determined by atomic absorption spectroscopy (AAS) and by electrospray ionization mass spectrometry (ESI-MS), and is resistant to digestion by snake venom phosphodiesterase. Treatment of the adduct with sodium cyanide regenerates TpT. Similar adduct formation was observed when T(pT) 8 was treated with cisplatin, but not when the phosphodiester linkages of T(pT) 8 were replaced with methylphosphonate groups. These results suggest that the platinum may be coordinated with the oxygens of the thymine and possibly with those of the phosphodiester group. As expected reaction of a 9-mer containing a -GTG-sequence with cisplatin yielded an adduct that contained a 1,3-Pt-GTG intrastrand cross-link. However, we found that the number and placement of phosphodiesters surrounding a -GTG-sequence significantly affected intrastrand cross-link formation. Increasing the number of negatively charged phosphodiesters in the oligonucleotide, increased the amount of -GTGplatination. Surrounding the -GTG-sequence with non-ionic methylphosphonate linkages reduced or eliminated cross-link formation. These observations suggest that interactions between cisplatin and the negatively charged phosphodiester backbone may play an important role in facilitating platination of guanine nucleotides in DNA.Reactions of the chemotherapeutic drug cis-diamminedichloroplatinum(II) (cisplatin or cis-DDP) with DNA have been studied for many years. Although it is widely accepted that the therapeutically relevant lesion is a 1,2-Pt-GG intrastrand cross-link, which links the N7s of the two guanines (1-3), the precise pathway leading to formation of this cross-link, as well as to 1,3-Pt-GNG intrastrand and G-G interstrand cross-links, is still under investigation. It is thought that cis-DDP is converted to cis-diamminediaquaplatinum(II) upon leaving the high concentration of chloride in the blood and entering the low concentration of chloride in the cell (3)(4)(5). This dicationic, aquated species then reacts with the DNA bases and other nucleophiles within the cell. While the reactions of cisplatin with nucleobases have been studied extensively, interactions with the DNA backbone have been largely overlooked. Platinum, a "soft" metal, preferentially binds to other "soft" ligands, such as amines and thiols (6,7). This binding preference does not, however, exclude the possibility that platinum can for...
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