Short hydrogen bonds enhance nonaromatic protein-related fluorescence.

Fluorescence in biological systems is usually associated with the presence of aromatic groups. Here, by employing a combined experimental and computational approach, we show that specific hydrogen bond networks can significantly affect fluorescence. In particular, we reveal that the single amino acid L-glutamine, by undergoing a chemical transformation leading to the formation of a short hydrogen bond, displays optical properties that are significantly enhanced compared with L-glutamine itself. Ab initio molecular dynamics simulations highlight that these short hydrogen bonds prevent the appearance of a conical intersection between the excited and the ground states and thereby significantly decrease nonradiative transition probabilities. Our findings open the door to the design of new photoactive materials with biophotonic applications.

Exercise, diet, and sleep habits of nurses working full-time during the COVID-19 pandemic: An observational study.

BACKGROUND: Healthy diet, exercise, and sleep practices may mitigate stress and prevent illness. However, lifestyle behaviors of acute care nurses working during stressful COVID-19 surges are unclear. PURPOSE: To quantify sleep, diet, and exercise practices of 12-hour acute care nurses working day or night shift during COVID-19-related surges. METHODS: Nurses across 10 hospitals in the United States wore wrist actigraphs and pedometers to quantify sleep and steps and completed electronic diaries documenting diet over 7-days. FINDINGS: Participant average sleep quantity did not meet national recommendations; night shift nurses (n = 23) slept significantly less before on-duty days when compared to day shift nurses (n = 34). Proportionally more night shift nurses did not meet daily step recommendations. Diet quality was low on average among participants. DISCUSSION: Nurses, especially those on night shift, may require resources to support healthy sleep hygiene, physical activity practices, and diet quality to mitigate stressful work environments.

Highly efficient luminescence from space-confined charge-transfer emitters.

Charge-transfer (CT) complexes, formed by electron transfer from a donor to an acceptor, play a crucial role in organic semiconductors. Excited-state CT complexes, termed exciplexes, harness both singlet and triplet excitons for light emission, and are thus useful for organic light-emitting diodes (OLEDs). However, present exciplex emitters often suffer from low photoluminescence quantum efficiencies (PLQEs), due to limited control over the relative orientation, electronic coupling and non-radiative recombination channels of the donor and acceptor subunits. Here, we use a rigid linker to control the spacing and relative orientation of the donor and acceptor subunits, as demonstrated with a series of intramolecular exciplex emitters based on 10-phenyl-9,10-dihydroacridine and 2,4,6-triphenyl-1,3,5-triazine. Sky-blue OLEDs employing one of these emitters achieve an external quantum efficiency (EQE) of 27.4% at 67 cd m-2 with only minor efficiency roll-off (EQE = 24.4%) at a higher luminous intensity of 1,000 cd m-2. As a control experiment, devices using chemically and structurally related but less rigid emitters reach substantially lower EQEs. These design rules are transferrable to other donor/acceptor combinations, which will allow further tuning of emission colour and other key optoelectronic properties.

A Simple Molecular Design Strategy for Delayed Fluorescence toward 1000 nm.

Harnessing the near-infrared (NIR) region of the electromagnetic spectrum is exceedingly important for photovoltaics, telecommunications, and the biomedical sciences. While thermally activated delayed fluorescent (TADF) materials have attracted much interest due to their intense luminescence and narrow exchange energies (ΔEST), they are still greatly inferior to conventional fluorescent dyes in the NIR, which precludes their application. This is because securing a sufficiently strong donor-acceptor (D-A) interaction for NIR emission alongside the narrow ΔEST required for TADF is highly challenging. Here, we demonstrate that by abandoning the common polydonor model in favor of a D-A dyad structure, a sufficiently strong D-A interaction can be obtained to realize a TADF emitter capable of photoluminescence (PL) close to 1000 nm. Electroluminescence (EL) at a peak wavelength of 904 nm is also reported. This strategy is both conceptually and synthetically simple and offers a new approach to the development of future NIR TADF materials.

Low energy optical excitations as an indicator of structural changes initiated at the termini of amyloid proteins.

There is a growing body of experimental work showing that protein aggregates associated with amyloid fibrils feature intrinsic fluorescence. In order to understand the microscopic origin of this behavior observed in non-aromatic aggregates of peptides and proteins, we conducted a combined experimental and computational study on the optical properties of amyloid-derived oligopeptides in the near-UV region. We have focused on a few model systems having charged termini (zwitterionic) or acetylated termini. For the zwitterionic system, we were able to simulate the longer tail absorption in the near UV (250-350 nm), supporting the experimental results in terms of excitation spectra. We analyzed the optical excitations responsible for the low-energy absorption and found a large role played by charge-transfer states around the termini. These charge-transfer excitations are very sensitive to the conformation of the peptide and in realistic fibrils may involve inter and intra chain charge reorganization.

Luminescent Gold(III) Thiolates: Supramolecular Interactions Trigger and Control Switchable Photoemissions from Bimolecular Excited States.

A new family of cyclometallated gold(III) thiolato complexes based on pyrazine-centred pincer ligands has been prepared, (C^Npz ^C)AuSR, where C^Npz ^C=2,6-bis(4-But C6 H4 )pyrazine dianion and R=Ph (1), C6 H4 tBu-4 (2), 2-pyridyl (3), 1-naphthyl (1-Np, 4), 2-Np (5), quinolinyl (Quin, 6), 4-methylcoumarinyl (Coum, 7) and 1-adamantyl (8). The complexes were isolated as yellow to red solids in high yields using mild synthetic conditions. The single-crystal X-ray structures revealed that the colour of the deep-red solids is associated with the formation of a particular type of short (3.2-3.3 Å) intermolecular pyrazine⋅⋅⋅pyrazine π-interactions. In some cases, yellow and red crystal polymorphs were formed; only the latter were emissive at room temperature. Combined NMR and UV/Vis techniques showed that the supramolecular π-stacking interactions persist in solution and give rise to intense deep-red photoluminescence. Monomeric molecules show vibronically structured green emissions at low temperature, assigned to ligand-based 3 IL(C^N^C) triplet emissions. By contrast, the unstructured red emissions correlate mainly with a 3 LLCT(SR→{(C^Npz ^C)2 }) charge transfer transition from the thiolate ligand to the π⋅⋅⋅π dimerized pyrazine. Unusually, the π-interactions can be influenced by sample treatment in solution, such that the emissions can switch reversibly from red to green. To our knowledge this is the first report of aggregation-enhanced emission in gold(III) chemistry.

Carbene metal amide photoemitters: tailoring conformationally flexible amides for full color range emissions including white-emitting OLED.

Conformationally flexible "Carbene-Metal-Amide" (CMA) complexes of copper and gold have been developed based on a combination of sterically hindered cyclic (alkyl)(amino)carbene (CAAC) and 6- and 7-ring heterocyclic amide ligands. These complexes show photoemissions across the visible spectrum with PL quantum yields of up to 89% in solution and 83% in host-guest films. Single crystal X-ray diffraction and photoluminescence (PL) studies combined with DFT calculations indicate the important role of ring structure and conformational flexibility of the amide ligands. Time-resolved PL shows efficient delayed emission with sub-microsecond to microsecond excited state lifetimes at room temperature, with radiative rates exceeding 106 s-1. Yellow organic light-emitting diodes (OLEDs) based on a 7-ring gold amide were fabricated by thermal vapor deposition, while the sky-blue to warm-white mechanochromic behavior of the gold phenothiazine-5,5-dioxide complex enabled fabrication of the first CMA-based white light-emitting OLED.

Efficient and Stable Deep-Blue Fluorescent Organic Light-Emitting Diodes Employing a Sensitizer with Fast Triplet Upconversion.

Multiple donor-acceptor-type carbazole-benzonitrile derivatives that exhibit thermally activated delayed fluorescence (TADF) are the state of the art in efficiency and stability in sky-blue organic light-emitting diodes. However, such a motif still suffers from low reverse intersystem crossing rates (kRISC ) with emission peaks <470 nm. Here, a weak acceptor of cyanophenyl is adopted to replace the stronger cyano one to construct blue emitters with multiple donors and acceptors. Both linear donor-π-donor and acceptor-π-acceptor structures are observed to facilitate delocalized excited states for enhanced mixing between charge-transfer and locally excited states. Consequently, a high kRISC of 2.36 × 106 s-1 with an emission peak of 456 nm and a maximum external quantum efficiency of 22.8% is achieved. When utilizing this material to sensitize a blue multiple-resonance TADF emitter, the corresponding device simultaneously realizes a maximum external quantum efficiency of 32.5%, CIEy ≈ 0.12, a full width at half maximum of 29 nm, and a T80 (time to 80% of the initial luminance) of > 60 h at an initial luminance of 1000 cd m-2 .

Highly efficient blue organic light-emitting diodes based on carbene-metal-amides.

Carbene-metal-amides are soluble and thermally stable materials which have recently emerged as emitters in high-performance organic light-emitting diodes. Here we synthesise carbene-metal-amide photoemitters with CF3-substituted ligands to show sky-blue to deep-blue photoluminescence from charge-transfer excited states. We demonstrate that the emission colour can be adjusted from blue to yellow and observe that the relative energies of charge transfer and locally excited triplet states influence the performance of the deep-blue emission. High thermal stability and insensitivity to aggregation-induced luminescence quenching allow us to fabricate organic light-emitting diodes in both host-free and host-guest architectures. We report blue devices with a peak external quantum efficiency of 17.3% in a host-free emitting layer and 20.9% in a polar host. Our findings inform the molecular design of the next generation of stable blue carbene-metal-amide emitters.

Efficient Vacuum-Processed Light-Emitting Diodes Based on Carbene-Metal-Amides.

Efficient vacuum-processed organic light-emitting diodes are fabricated using a carbene-metal-amide material, CMA1. An electroluminescence (EL) external quantum efficiency of 23% is achieved in a host-free emissive layer comprising pure CMA1. Furthermore external quantum efficiencies of up to 26.9% are achieved in host-guest emissive layers. EL spectra are found to depend on both the emissive-layer doping concentration and the choice of host material, enabling tuning of emission color from mid-green (Commission Internationale de l'Éclairage co-ordinates [0.24, 0.46]) to sky blue ([0.22 0.35]) without changing dopant. This tuning is achieved without compromising luminescence efficiency (>80%) while maintaining a short radiative lifetime of triplets (<1 µs).

The cerebrospinal fluid production rate is reduced in dementia of the Alzheimer's type.

OBJECTIVE: To evaluate the production rate of CSF in patients with differing disease states. METHODS: The authors measured the production rate of CSF in three groups of patients: five patients with PD below age 60 (aged 51 +/- 4 years, mean +/- SD), nine with PD over age 60 (aged 69 +/- 6 years, mean +/- SD), and seven with dementia of the Alzheimer's type (AD) (aged 72 +/- 9 years, mean +/- SD). This method, based on the Masserman technique, employs ventricular rather than a lumbar access to the CSF space. Furthermore, the volume of CSF removed during the procedure is only 3 mL rather than 10 mL. RESULTS: These measurements indicate that the mean rate of CSF production in patients with PD under age 60 was 0.47 +/- 0.13 mL/minute, in patients with PD aged 60 or older the mean rate was 0.40 +/- 0.12 mL/minute, and in patients with AD the mean rate was 0.20 +/- 0.06 mL/minute. CONCLUSION: These results indicate that the rate of CSF production in patients with PD is normal, and that the rate of CSF production in patients with AD is markedly reduced.

Assessment of low-flow CSF drainage as a treatment for AD: results of a randomized pilot study.

OBJECTIVE: This prospective, randomized, controlled study was designed to investigate the safety, feasibility, and preliminary efficacy of long-term CSF drainage via a low-flow ventriculoperitoneal shunt in subjects suffering from AD. METHODS: Twenty-nine subjects selected for probable AD (National Institute of Neurological and Communicative Diseases and Stroke-Alzheimer's Disease and Related Dementias Association criteria) were screened to exclude normal pressure hydrocephalus or other etiologies of dementia and randomized to treatment (shunt) or no treatment groups. The study endpoint was the comparison of group performance on psychometric testing at quarterly intervals for 1 year. Shunted subjects had CSF withdrawn for MAP-tau and Abeta((1-42)) assays at the same time intervals. RESULTS: There was no mortality from the surgical procedure, and no patient sustained a subdural hematoma. Five notable postoperative adverse events, which resolved without permanent neurologic deficit, were reported in the shunt group. Group mean Mattis Dementia Rating Scale total scores showed little change over the year in the shunt-treatment group, in contrast to a decline in the control group (p = 0.06). Mini-Mental State Examination mean scores supported a trend in favor of shunt treatment (p = 0.1). There was a concomitant decrease in ventricular CSF concentrations of AD biomarkers MAP-tau and Abeta((1-42)). CONCLUSIONS: The surgical procedure and the device are reasonably safe. Adverse events were consistent with shunt procedures for hydrocephalus in this older population. The endpoint data show a trend in favor of the treated group. A larger, randomized, double-blinded, controlled, clinical trial is underway.

Use of high frequency jet ventilation during mechanical hyperventilation to reduce intracranial pressure in patients with multiple organ system injury.

Eleven patients with multiple organ system injury, including significant closed head injury, all required positive end-expiratory pressure (PEEP) for treatment of their pulmonary pathological condition. Additionally, the need for intracranial pressure (ICP) monitoring had previously been established on clinical evaluation by the Neurosurgery Service. Seven of the 11 patients met the criteria for invasive hemodynamic monitoring. Hemodynamic monitoring data are supplied for these 7 patients. All patients, after the initial institution of conventional means of hyperventilation, were transitioned to high frequency jet ventilation (HFJV) to evaluate the effects of HFJV during mechanical hyperventilation. There was a statistically significant decrease in ICP (mean decrease of 7.2 mm Hg). There was also a statistically significant fall in PaO2 from 131 to 101 torr. This was not associated with an appreciable decrease in oxygen delivery. There was no change in cardiac output or intrapulmonary shunt fraction. It is concluded that successful control of ICP was possible in all cases without impairment of cardiac output, oxygen delivery, or cerebral perfusion pressure, even when the pulmonary abnormality required the use of PEEP.

Effect of intracranial pressure monitoring and aggressive treatment on mortality in severe head injury.

During 1977-1978, 127 patients with severe head injury were admitted and underwent intracranial pressure (ICP) monitoring. All patients had Glasgow Coma Scale (GCS) scores of 7 or less. All received identical initial treatment according to a standardized protocol. The patients' average age was 29 years; 60% had multiple trauma, and 35% needed emergency intracranial operations. Treatment for elevations of ICP was begun when ICP rose to 20 to 25 mm Hg, and included mannitol therapy and drainage of cerebrospinal fluid (CSF) when possible. Forty-three patients (34%) had ICP greater than or equal to 25 mm Hg; of these, 36 (84%) died. The mortality rate of the entire group was 46%. During 1979-1980, 106 patients with severe head injury were admitted and underwent ICP monitoring. Their average ager was 29 years; 51% had multiple trauma, and 31% underwent emergency intracranial surgery. All patients received the same standardized protocol as the previous series, with the exception of the treatment of ICP. In this present series: if ICP was 15 mm Hg or less (normal ICP), patients were continued on hyperventilation, steroids, and intensive care; if ICP was 16 to 24 mm Hg, mannitol was administered and CSF was drained; if ICP was 25 mm Hg or greater, the patients were randomized into a controlled barbiturate therapy study. Twenty-six patients (25%) had ICP's of 25 mm Hg or greater, compared to 34% in the previous series (p less than 0.05), and 18 of these 26 patients (69%) died. The overall mortality for this current series was 28% compared to 46% in the previous series (p less than 0.0005). This study reconfirms the high mortality rate if ICP is 25 mm Hg or greater; however, the data also document that early aggressive treatment based on ICP monitoring significantly lessens the incidence of ICP of 25 mm Hg or greater and reduces the overall mortality rate of severe head injury.

Steroids in severe head injury: A prospective randomized clinical trial.

This is a prospective randomized study of the efficacy of steroid therapy in patients with severe head injury. One hundred patients were randomized into two equal groups: the steroid group received 5 mg/kg/day of methylprednisolone, and the nonsteroid group received no drug. The groups were similar in their clinical features. All patients received a standardized therapeutic regimen. The patients were also classified as early responders or nonresponders to the overall treatment protocol without regard to steroid administration, on the basis of change in Glasgow Coma Scale score during the first 3 days of admission. There was no statistically significant difference in the outcome of the steroid and nonsteroid group at 6 months. Of the responders who were on steroids, 74% had good outcomes or were disabled, compared with 56% of the responders who did not receive steroids. In the nonresponder group, the patients on steroids were actually associated with a worse outcome than those who did not receive steroids: 75% of the nonresponders who received steroids were dead or vegetative, compared to 56% of those who were not receiving steroids. The data suggest that: 1) the effect of steroids may be different for different patient groups; 2) in order to identify these patients, a sensitive coma scale is needed; and 3) a rational approach to steroid therapy in head-injured patients may be to start all patients on steroids, but to discontinue their use in patients identified as not benefiting from steroid therapy.

Posterior segmental spinal instrumentation (PSSI) with posterolateral decompression and debulking for metastatic thoracic and lumbar spine disease. Limitations of the technique.

Twenty-five patients with metastatic thoracic and lumbar spine disease were initially treated by the authors with posterolateral debridement and decompression, along with posterior segmental spinal instrumentation. Ten patients had marked paresis, nine had signs of spinal cord or cauda equina compression without paresis, and all patients had pain severe enough to prevent sitting/standing/walking. The posterior approach was used in these patients instead of an anterior one because of translocation (4), three-column disease (16), three or more vertebral bodies involved (13), disease at two separate locations (2), and inability to tolerate an anterior approach (3). All patients had maintenance of spinal alignment for the length of follow-up or until their ultimate demise. Good pain relief was achieved in 19 of 25 patients. Six of ten patients with significant paresis recovered. Four patients developed recurrent spinal cord compression within 12 months postoperative from regrowth of tumor that was not controlled by radiotherapy or chemotherapy. Six of the 25 patients were not significantly palliated by the technique.

Intracranial pressure monitoring in patients with severe head injury.

Increased intracranial pressure (ICP) has an adverse effect on the clinical course of patients with severe head injuries. Direct intracranial measurement is the only method of knowing the precise ICP. At the Maryland Institute for Emergency Medical Services Systems, elevations in ICP are treated according to an aggressive protocol. Our experience with this protocol has led to the following conclusions: 1) ICPs above 25 mm Hg are associated with an unacceptable mortality, 2) aggressive medical treatment of patients with an ICP of 16 mm Hg can decrease the number of patients whose ICPs reach 25 mm Hg, and 3) the overall mortality of severe head injury can be reduced with such a protocol. ICP monitoring can be a valuable parameter in the management of severe head injury. With continuous accurate reading of ICP, sound theraputic decisions can be made about the patient's care that, ultimately, can effect the patient's survival and outcome.

Immediate mini-myelography in acute cervical cord injuries.

The use of contrast myelography in the evaluation of acute cervical spinal cord trauma is controversial. The purpose of employing such a technique is to demonstrate any persistent extradural cord compression after the spine is realigned by skeletal traction. The surgical correction of such compression may result in enhanced neurological recovery. The "mini-myelogram" is accomplished by performing a lateral C1/C2 spinal puncture and injecting a low volume of Pantopaque into the subarachnoid space. Demonstration of significant extradural compression results in emergency surgery for appropriate decompression. A small percentage of patients may enjoy enhanced recovery due to the decompression. A description of the technique and results of 90 patients undergoing mini-myelography are presented.

Exercise capacity and Doppler pressure measurements in symptomatic peripheral arterial obstructive disease.

BACKGROUND: Doppler pressure measurements are a useful diagnostic tool in peripheral arterial obstructive disease. The aim of our study was to determine whether these pressure values do predict the degree of impairment of the walking capacity in symptomatic patients. PATIENTS AND METHODS: We compared the claudication distances (CDI: initial claudication distance, CDA: absolute claudication distance) of 939 patients (63 +/- 11 years) with stable intermittent claudication (Fontaine IIb) with the ankle pressure values at rest (APR) and after exercise (APE), with the ankle/brachial pressure index at rest (ABIR) and after exercise (ABIE), and with the ratio (ABIRATIO = ABIE/ABIR). Ankle systolic pressures were obtained using an 8 MHz Doppler probe. CD was measured by a treadmill test at constant-load conditions (3 km/hr; inclination 12%). Brachial systolic pressures were obtained using an automated blood pressure monitor. The values of the objectively worse leg were correlated with CDI and CDA. RESULTS: Low Doppler pressure values were not accompanied by significantly shorter walking distances in symptomatic patients. The resting pressure values (APR, ABIR) did not correlate with the claudication distances (CDI: 54 +/- 31 m; CDA: 87 +/- 41 m). For the exercise values (APE, ABIE), even a very slight inverse correlation with the claudication distances was found. In addition, the correlation between the pressure index ratio and the walking distances (ABIRATIO vs. CDI: r = -0.25, p < 0.01; ABIRATIO vs. CDA: r = -0.20, p < 0.01) was inverse, too, but slightly more pronounced. CONCLUSIONS: In patients with intermittent claudication the ankle artery pressures and the indices derived from these pressure values do not predict the walking distance. Therefore, the decision for angioplasty or bypass surgery should be made with regards to the impairment of quality of life rather than Doppler pressure values.