Cyano-tryptophans as dual infrared and fluorescence spectroscopic labels to assess structural dynamics in proteins

The steady state and time-resolved fluorescence and infrared (IR) properties of 4- and 5-cyanotryptophan (CNTrp) are investigated and compared, and the tryptophan (Trp) analogs are found to be very attractive to study structural and dynamic properties of proteins. The position of the nitrile substitution as well as the solvent environment influences the spectroscopic properties (solvatochromism). Similar to native Trp, electronic (nanosecond) lifetime and emission spectra are modulated by the environment, making CNTrps attractive fluorescent probes to study the structural dynamics of proteins in complex media. The nitrile absorption in the IR region can provide local structural information as it responds sensitively to changes in electrostatics and hydrogen bond (HB) interactions. Importantly, we find that 4CNTrp exhibits a single absorption in the nitrile stretch region, while the model compound 4CN-indole (4CNI) shows two. Even though the spectrum of the model compound is perturbed by a Fermi resonance, we find that 4CNTrp itself is a useful IR label. Moreover, if the nitrile group is substituted at the 5 position, the Trp analog predominantly reports on its HB status. Because the current literature on similar compounds is too limited for a detailed solvatochromic analysis, we extend the available data significantly. Only now are microscopic details such as the mentioned sensitivity to electrostatics coming to light. The vibrational lifetime of the CN moiety (acting on a picosecond time scale in contrast to the nanosecond time scale for fluorescent emission) allows for its application in 2D-IR spectroscopy in the low picosecond range. Taken together, the benefits of CNTrps are that they absorb and emit separately from the naturally occurring Trp and that in these dual fluorescence/vibrational labels, observables of IR and fluorescence spectroscopy are modulated differently by their surroundings. Because IR absorption and fluorescence operate on different time and length scales, they thus provide complementary structural information.</p

Vibrational Spectroscopic Map, Vibrational Spectroscopy, and Intermolecular Interaction

© 2020 American Chemical Society. Vibrational spectroscopy is an essential tool in chemical analyses, biological assays, and studies of functional materials. Over the past decade, various coherent nonlinear vibrational spectroscopic techniques have been developed and enabled researchers to study time-correlations of the fluctuating frequencies that are directly related to solute-solvent dynamics, dynamical changes in molecular conformations and local electrostatic environments, chemical and biochemical reactions, protein structural dynamics and functions, characteristic processes of functional materials, and so on. In order to gain incisive and quantitative information on the local electrostatic environment, molecular conformation, protein structure and interprotein contacts, ligand binding kinetics, and electric and optical properties of functional materials, a variety of vibrational probes have been developed and site-specifically incorporated into molecular, biological, and material systems for time-resolved vibrational spectroscopic investigation. However, still, an all-encompassing theory that describes the vibrational solvatochromism, electrochromism, and dynamic fluctuation of vibrational frequencies has not been completely established mainly due to the intrinsic complexity of intermolecular interactions in condensed phases. In particular, the amount of data obtained from the linear and nonlinear vibrational spectroscopic experiments has been rapidly increasing, but the lack of a quantitative method to interpret these measurements has been one major obstacle in broadening the applications of these methods. Among various theoretical models, one of the most successful approaches is a semiempirical model generally referred to as the vibrational spectroscopic map that is based on a rigorous theory of intermolecular interactions. Recently, genetic algorithm, neural network, and machine learning approaches have been applied to the development of vibrational solvatochromism theory. In this review, we provide comprehensive descriptions of the theoretical foundation and various examples showing its extraordinary successes in the interpretations of experimental observations. In addition, a brief introduction to a newly created repository Web site (http://frequencymap.org) for vibrational spectroscopic maps is presented. We anticipate that a combination of the vibrational frequency map approach and state-of-the-art multidimensional vibrational spectroscopy will be one of the most fruitful ways to study the structure and dynamics of chemical, biological, and functional molecular systems in the future

Rozwiązania umożliwiające bezpieczniejsze loty w środowisku o ograniczonej widoczności

Recent combat experience in Operation Enduring Freedom and Iraqi Freedom has once again demonstrated the unforgiving nature ofthe desert environment. Thetotal loss of aircraft, and near losses resulting in major damage, from a uniąue helicopter condition called "brownout" is disproportional to actual combat losses. Fully operational aircraft are routinely destroyed due to the loss ofvisual reference resulting from brownouts. This phenomenon is not new to rotory wing aviation but has now become a focal point of aviation commands as a problem to be sohed. This paper puts forth seyeral potential solutions that challenge our industry to provide a comprehensive answer to an urgent problem. The paper will address steps we can take now and in the future to improve a pilot's situational awareness and reduce the risk encountered during brownout events. Near term solutions represent more easily retrofitable elements that do not require a large amount of aircraft integration. These include sensor and display updates and modernized control laws. In the longer term advantage can be taken of the greater control authority afforded by Fly-By-Wire systems andfurther improvements in sensor technology.Ostatnie doświadczenia wyniesione z Operacji Umacniania Wolności i Wolność Irakowi jeszcze raz podkreśliły surowość środowiska pustynnego. Całkowite straty statków powietrznych i bliskie całkowitej utracie poważne uszkodzenia zdolności operacyjnej śmigłowców wskutek zaniku widoczności są nieporównywalnie duże w stosunku do całowitych strat w boju. Statki powietrzne będące w całkowitej zdolności operacyjnej bywają systematycznie uszkadzane wskutek utraty wizualnego źródła danych na skutek spadku widoczności. Owo zjawisko nie jest niczym nowym dla wiropłatów, lecz obecnie stało się obiektem zainteresowania dowódców lotnictwa, jako problem do rozwiązania. W artykule przedstawiono kilka potencjalnych rozwiązań stnowiących wyzwanie dla naszego przemysłu, przedsięwzięć kompleksowych działań celem odpowiedzi na nurtujący problem. Pokazano poszczególne kroki, jakie możemy podjąć teraz i w przyszłości, aby poprawić możliwość orientowania się w sytuacji przez pilota oraz zmniejszyć ryzyko w trakcie zaników widoczności. Jako rozwiązania proponuje sie wymiane elementów na nowe, które nie wymagają skomplikowanej integracji z systemami płatowca. Rozwiązania również obejmują aktualizację czujników, wyświetlaczy i modernizacji charakterystyk sterowania. W dalszej perspektywie czasowej można odnieść korzyści ze zwiększenia znaczenia elektronicznego układu sztucznej stateczności i sterowania oraz dalszych udoskonaleń czujników