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PURPOSE: The United States is rapidly becoming a more multicultural society. Although minority groups are the fastest growing segment of the U.S. population, minorities are not pursuing careers in health care professions in the same proportions. The literature suggests that increasing the number of minorities in the health care professions will increase access to health care for minority populations and help non-minority health care professionals become more aware of and sensitive to minority issues. The results reported here are part of a larger national survey that examined the commitment of entry-level dental hygiene programs to ethnic/racial diversity. METHODS: A 19-item survey was mailed in 1998 to all 233 entry-level dental hygiene program directors in the United States. The survey was piloted using a random sample of six entry-level dental hygiene program directors in the United States. Data were collected on demographics, formal written mission statements that support ethnic/racial diversity, minority recruitment programs, and recruitment mechanisms. Data were analyzed using frequencies, chi-square, t-tests, F-tests and Pearson correlation coefficients. The response rate was 60.1% (140). RESULTS: Results indicate that 10.5% of dental hygiene students and 6.7% of dental hygiene faculty are members of ethnic/racial minorities. Results also indicate that Asian and Pacific Islander (API) students are not underrepresented in U.S. entry-level dental hygiene programs, but Asian and Pacific Islander faculty are. CONCLUSIONS: A statistically significant relationship was found between the percentage of 1) minority faculty and students in entry-level dental hygiene programs; and 2) minority students and minorities in the state where the entry-level dental hygiene program resides. [ABSTRACT FROM AUTHOR]

Purpose Forty-two states to date have passed legislation to expanded the role of dental hygienists for improved access to basic oral health services for underserved populations. Recent legislative changes in the state of Kansas have created the Extended Care Permit (ECP) I, II, and III designations. The purpose of this study was to examine the experiences of registered dental hygienists in Kansas holding ECP III certificates. Methods Secondary data analysis was performed utilizing data collected from an ECP provider survey conducted in 2021. Dental hygienists in Kansas holding an Extended Care Permit III (n=88) were sent a 39-item electronic survey and informed consent was obtained prior to beginning the survey. Descriptive data analyses consisted of frequency distributions and percentages. Inferential data analysis consisted of Fisher's Exact and Chi-Square tests to evaluate associations between ECP III demographics, practice characteristics, and services provided. Results A total of 22 responses were received for a 25% response rate. The majority of the respondents (77%) were employed by a Safety Net Clinic. The practice settings reporting the highest percentage of ECP III services during the period of data collection were school-based settings, using portable equipment (68%). No associations were found between ECP III personal and practice characteristics and the provision of services specific to the ECP III permit. Conclusion Results suggest that a low percentage of ECP III permit holders are providing ECP III-specific services. Considering these findings and the outcomes of previous studies, there is speculation that barriers continue to exist that prevent permit holders from performing ECP III-specific services and providing dental hygiene services to the fullest extent of an ECP license., (Copyright © 2023 The American Dental Hygienists’ Association.)

Ocean acidification (OA) impacts the survival, fertilization, and community structure of marine organisms across the world. However, some populations or species are considered more resilient than others, such as those that are invasive, globally distributed, or biofouling. Here, we tested this assumption by investigating the effect of pH on the larval development of one such tunicate, Ciona robusta , which is currently exposed to a wide range of pH levels. Consistent with our hypothesis, C. robusta larvae developed and metamorphosed at a rate comparable to control (pH 8.0) at modest near-future conditions (pH 7.7) over a 58-hour period. However, development was stunted at the extreme low pH of 6.8 such that no embryo progressed beyond late cleavage after 58 hours. Interestingly, piecewise regression of the proportion of embryos at the most advanced stage at a given time point against pH identified a breakpoint with the highest pH (~pH 7.6) at around hatching. The variation in breakpoint pH throughout ontogeny highlighted that the sensitivity to decreasing pH differs significantly between developmental stages. More broadly, our results show that even a cosmopolitan, biofouling, invasive species could be negatively impacted by decreasing pH.

As the number of prescriptions, over-the-counter medications and drugs of abuse continue to increase, forensic laboratories are faced with the challenge of developing more comprehensive screening methods in order to detect them in whole blood samples. Another challenge faced by forensic laboratories is detecting and identifying novel synthetic compounds as they emerge and change. Traditional drug screening methods include enzyme immunoassay (EIA) and either gas or liquid chromatography paired with mass spectrometry (GC-MS or LC-MS-MS, respectively). While these methods are good, they have their disadvantages. For example, EIA requires special reagents for each drug class, GC-MS requires extensive sample preparation, and LC-MS-MS only detects drugs on a known inclusion lists of compounds of interest. Described here is the development of a robust and comprehensive screening method for drugs in whole blood samples that eliminates the aforementioned disadvantages of the traditional methods. Using a Q Exactive Focus™ liquid chromatography-high-resolution accurate mass spectrometer (LC-HRMS-MS), a method was developed that is capable of detecting ~200 drugs at a concentration of 2 μg/L for most analytes. This method also employs a more automated data processing feature which reduces processing time. Finally, it has the added benefit of retroactive data analysis, which allows it to be used for unknown drug analysis as well. Used as an initial screening method, the comprehensive drug screen using LC-HRMS-MS has the potential to take on two of the most important challenges faced by forensic laboratories today., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Multiple national and international trends and drivers are radically changing what biological security means for the United Kingdom (UK). New technologies present novel opportunities and challenges, and globalisation has created new pathways and increased the speed, volume and routes by which organisms can spread. The UK Biological Security Strategy (2018) acknowledges the importance of research on biological security in the UK. Given the breadth of potential research, a targeted agenda identifying the questions most critical to effective and coordinated progress in different disciplines of biological security is required. We used expert elicitation to generate 80 policy-relevant research questions considered by participants to have the greatest impact on UK biological security. Drawing on a collaboratively-developed set of 450 questions, proposed by 41 experts from academia, industry and the UK government (consulting 168 additional experts) we subdivided the final 80 questions into six categories: bioengineering; communication and behaviour; disease threats (including pandemics); governance and policy; invasive alien species; and securing biological materials and securing against misuse. Initially, the questions were ranked through a voting process and then reduced and refined to 80 during a one-day workshop with 35 participants from a variety of disciplines. Consistently emerging themes included: the nature of current and potential biological security threats, the efficacy of existing management actions, and the most appropriate future options. The resulting questions offer a research agenda for biological security in the UK that can assist the targeting of research resources and inform the implementation of the UK Biological Security Strategy. These questions include research that could aid with the mitigation of Covid-19, and preparation for the next pandemic. We hope that our structured and rigorous approach to creating a biological security research agenda will be replicated in other countries and regions. The world, not just the UK, is in need of a thoughtful approach to directing biological security research to tackle the emerging issues., Competing Interests: Authors TM and HS are affiliated with Opencell. KM is affiliated with Biosecure Ltd. Arcadia provided support in the form of salaries for authors WS and CR. There are no patents, products in development or marketed products to declare. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Horizon scanning is intended to identify the opportunities and threats associated with technological, regulatory and social change. In 2017 some of the present authors conducted a horizon scan for bioengineering (Wintle et al., 2017). Here we report the results of a new horizon scan that is based on inputs from a larger and more international group of 38 participants. The final list of 20 issues includes topics spanning from the political (the regulation of genomic data, increased philanthropic funding and malicious uses of neurochemicals) to the environmental (crops for changing climates and agricultural gene drives). The early identification of such issues is relevant to researchers, policy-makers and the wider public., Competing Interests: LK, LA, CB, RB, RC, MD, AD, RH, LH, AM, CN, SÓ, NP, WP, VR, CR, CR, AR, PS, CS, LS, ET, GU, BW, NZ, WS No competing interests declared, NE Has received funding in the past five years from the following organizations to conduct research and speak on issues related to this article: Greenwall Foundation; Max Planck Institute for Evolutionary Biology; Davis Foundation; National Science Foundation. Has participated in the International Genetically Engineered Machine (iGem) competition as a judge and a member of the Safety Committee several times over the past five years. KH Has participated in the International Genetically Engineered Machine (iGem) competition as a judge and a member of the Safety Committee several times over the past five years; has accepted travel funding from the Max Planck Institute for Evolutionary Biology. TK Holds a grant from the Open Philanthropy Foundation to study DIYbio, including gene drives; member of the IUCN task force on synthetic biology and gene drives; co-chair of the human practices committee of iGEM; member of the biosafety/security advisory board for MIT Broad Foundry; has been affiliated with the Genetic Biocontrol of Invasive Rodents consortium at NC State but has never received any salary or other compensation. PM Co-founder of Biosecure Ltd. JN Listed as an inventor on multiple patents; most relevant patent is US 2019/0323022 A1 and family. Acted as a consultant to BASF (2014-2019). AO Director of the Industrial Biotechnology Alliance, Norwich Research Park; trustee with the New Phytologist Trust. MP Recipient of a grant and a gift from the Open Philanthropy Foundation to study biosecurity at Stanford university; volunteer director of the human practices committee of the international Genetically Engineered Machine (iGEM) Foundation; member of the board of directors of Revive & Restore. EP Holds shares in Celixir Ltd and Arkurity Ltd; has received payment from Deep Science Ventures Ltd, the Nuclear Threat Initiative, Revive & Restore, Celixir Ltd, Arkurity Ltd, CSIRO, International Union for the Conservation of Nature and Biosecure. DS, RS Involved in a consultancy for the ERA-CoBioTech programme (an ERA-Net network funded by Horizon 2020)., (© 2020, Kemp et al.)

The erosion of night-time by the introduction of artificial lighting constitutes a profound pressure on the natural environment. It has altered what had for millennia been reliable signals from natural light cycles used for regulating a host of biological processes, with impacts ranging from changes in gene expression to ecosystem processes.Studies of these impacts have focused almost exclusively on those resulting from stationary sources of light emissions, and particularly streetlights. However, mobile sources, especially road vehicle headlights, contribute substantial additional emissions.The ecological impacts of light emissions from vehicle headlights are likely to be especially high because these are (1) focused so as to light roadsides at higher intensities than commonly experienced from other sources, and well above activation thresholds for many biological processes; (2) projected largely in a horizontal plane and thus can carry over long distances; (3) introduced into much larger areas of the landscape than experience street lighting; (4) typically broad "white" spectrum, which substantially overlaps the action spectra of many biological processes and (5) often experienced at roadsides as series of pulses of light (produced by passage of vehicles), a dynamic known to have major biological impacts.The ecological impacts of road vehicle headlights will markedly increase with projected global growth in numbers of vehicles and the road network, increasing the local severity of emissions (because vehicle numbers are increasing faster than growth in the road network) and introducing emissions into areas from which they were previously absent. The effects will be further exacerbated by technological developments that are increasing the intensity of headlight emissions and the amounts of blue light in emission spectra. Synthesis and applications . Emissions from vehicle headlights need to be considered as a major, and growing, source of ecological impacts of artificial night-time lighting. It will be a significant challenge to minimise these impacts whilst balancing drivers' needs at night and avoiding risk and discomfort for other road users. Nonetheless, there is potential to identify solutions to these conflicts, both through the design of headlights and that of roads.

In this study, gravity waves (GWs) in the high-resolution GEOS-5 Nature Run are first evaluated with respect to satellite and other model results. Southern Hemisphere winter sources of non-orographic GWs in the model are then investigated by linking measures of tropospheric non-orographic gravity wave generation tied to precipitation and frontogenesis with absolute gravity wave momentum flux in the lower stratosphere. Finally, non-orographic GW momentum flux is compared to orographic gravity wave momentum flux and compared to previous estimates. The results show that the global patterns in GW amplitude, horizontal wavelength, and propagation direction are realistic compared to observations. However, as in other global models, the amplitudes are weaker and horizontal wavelengths longer than observed. The global patterns in absolute GW momentum flux also agree well with previous model and observational estimates. The evaluation of model non-orographic GW sources in the Southern Hemisphere winter shows that strong intermittent precipitation (greater than 10 mm h -1 ) is associated with GW momentum flux over the South Pacific, whereas frontogenesis and less intermittent, lower precipitation rates (less than 10 mm h -1 ) are associated with GW momentum flux near 60°S. In the model, orographic GWs contribute almost exclusively to a peak in zonal mean momentum flux between 70 and 75°S, while non-orographic waves dominate at 60°S, and non-orographic GWs contribute a third to a peak in zonal mean momentum flux between 25 and 30°S.

Purpose: The purpose of this study was to determine the degree to which U.S. dental hygiene programs are incorporating cultural competency education into the dental hygiene curriculum and to identify associated program characteristics., Methods: A 19 item survey was electronically administered to all 334 U.S. dental hygiene program directors. The questionnaire solicited information on teaching and evaluation methodologies relative to cultural competency education (CCE), as well as director's perceptions and program demographic information., Results: An overall response rate of 27% was obtained. The majority of participating programs (92%) reported incorporating CCE into the curriculum in some form. Most responding directors indicated that CCE has been effectively integrated into the curriculum. A variety of curricular methods are being employed to teach CCE with lectures being the most common method utilized. Results of this study suggest that an overwhelming number of responding programs (98%) participate in community outreach/service learning projects. However, nearly half (42%) indicated that their students are not evaluated for culture competency knowledge, skills and attitudes., Conclusion: These findings imply that responding programs are incorporating CCE into the curriculum using a variety of teaching methodologies with an emphasis on community outreach/service learning projects. It is important to consider whether or not community outreach/service learning projects improve dental hygiene students' cultural competency skills, attitudes and knowledge. Future research efforts should aim to describe the value and effectiveness of such programs at achieving cultural competence., (Copyright © 2016 The American Dental Hygienists’ Association.)

Purpose: The purpose of this study was to examine the challenges related to formal clinical remediation in dental hygiene programs, which include timing of student identification, policy development, and the issues of methodology and scheduling., Methods: A 23 item investigator-designed survey was electronically distributed to all 303 U.S. entry-level dental hygiene program directors. This questionnaire included 23 forced-choice questions with the options to add comments to 8 of the questions. A total of 111 surveys were returned yielding a response rate of 36%. Descriptive statistics and Chi-square analyses were utilized to analyze relationships between responses and the degree earned from the dental hygiene program., Results: All schools reported having a remediation policy; however, 13.6% of the respondents revealed this information was not readily available to students. The majority of respondents (67.8%) reported identifying students with clinical deficiencies in the preclinical semester, and 15.5% identified students in the second year, second clinical semester. Instrumentation technique was identified as the area in greatest need of remediation (81%), followed by critical thinking and problem solving skills (12%). Coordination of faculty and student schedules to conduct remediation was identified as one of the greatest challenges by respondents (25.2%). Results of this study suggest that challenges exist with the process of remediation. Some of these challenges include involving the student in remedial plan development, the academic consequences associated with remediation and scheduling time and space for remedial activities., Conclusion: These findings indicate that respondents are well aware of the need for remediation policies in dental hygiene programs. The point in time varies when students in need of remediation are identified. Therefore, further research needs to be conducted to determine the reasons for this difference. Some reasons may include inability to grasp the foundational skills and/or the complexity of advanced instrumentation in the second year. Also, it is suggested that investigation regarding methods used to address the challenge of faculty and student scheduling for remediation sessions would be useful.

Purpose: The purpose of this manuscript was to conduct a cost analysis of the Miles of Smiles Program, a collaboration between the University of Missouri-Kansas City School of Dentistry and the Olathe School District in Kansas. This preventive program was implemented to improve the access to oral health care for low income children within the school district., Methods: An inventory list and de-identified patient records were used to determine the costs associated with operating the program to serve 339 elementary school students during the 2008 to 2009 school term. Costs related to equipment, supplies and personnel were included. The costs were then compared to the amount of Medicaid reimbursement obtained for the services provided. Additionally, the cost of operating a similar program, if staffed by dental professionals rather than supervised dental hygiene students, was estimated., Results: The cost of operating the program during the 2008 to 2009 school term was $107,515.74. The program received Medicaid reimbursement for approximately 1.5% of the total operating cost of and approximately 6.3% of the total billable services, however, challenges with submitting and billing Medicaid claims for the first time contributed to this low rate of reimbursement. If a similar program that utilized dental professionals was implemented and treated the same number of patients, the cost would be approximately $37,529.65 more due to higher expenses associated with personnel and supplies., Conclusion: The program is not self-sustainable based on Medicaid government-funded insurance reimbursement alone, and therefore continuous external sources of funding or a change in the program design would be necessary for long-term sustainability of the program., (Copyright © 2014 The American Dental Hygienists’ Association.)

Purpose: The purpose of this manuscript was to conduct a cost analysis of the Miles of Smiles Program, a collaboration between the University of Missouri-Kansas City School of Dentistry and the Olathe School District in Kansas. This preventive program was implemented to improve the access to oral health care for low income children within the school district., Methods: An inventory list and de-identified patient records were used to determine the costs associated with operating the program to serve 339 elementary school students during the 2008 to 2009 school term. Costs related to equipment, supplies and personnel were included. The costs were then compared to the amount of Medicaid reimbursement obtained for the services provided. Additionally, the cost of operating a similar program, if staffed by dental professionals rather than supervised dental hygiene students, was estimated., Results: The cost of operating the program during the 2008 to 2009 school term was $107,515.74. The program received Medicaid reimbursement for approximately 1.5% of the total operating cost of and approximately 6.3% of the total billable services, however, challenges with submitting and billing Medicaid claims for the first time contributed to this low rate of reimbursement. If a similar program that utilized dental professionals was implemented and treated the same number of patients, the cost would be approximately $37,529.65 more due to higher expenses associated with personnel and supplies., Conclusion: The program is not self-sustainable based on Medicaid government-funded insurance reimbursement alone, and therefore continuous external sources of funding or a change in the program design would be necessary for long-term sustainability of the program.

Cyanovirin-N (CV-N) is a cyanobacterial lectin that binds to specific oligomannoses on the surface of gp120, resulting in nanomolar antiviral activity against HIV. In its monomeric form, CV-N contains two functional carbohydrate-binding domains, A and B. When refolded at high concentration, the protein can form a domain-swapped dimer. To clarify the role of multiple-binding sites in CV-N, we previously designed a monomeric mutant, P51G-m4-CVN, in which the binding site on domain A was rendered ineffective by four mutations (m4); in addition, a hinge region mutation (P51G) hinders the formation of a domain swapped dimer. The protein bound gp120 with diminished affinity and was completely inactive against HIV. Here, we present two mutants, DeltaQ50-m4-CVN and S52P-m4-CVN, which fold exclusively as domain-swapped dimers while containing the four mutations that abolish domain A. The dimers contain two intact B domains, thus restoring multivalency. DeltaQ50-m4-CVN and S52P-m4-CVN bind gp120 at low-nanomolar concentrations and recover in part the antiviral activity of wt CV-N. These results indicate that the number of carbohydrate binding domains, rather than their identity, is crucial to CV-N functionality., ((c) 2009 Wiley Periodicals, Inc.)

The use of liquid chromatography (LC) coupled with tandem mass spectrometry (MS/MS) or single-stage mass spectrometry (MS) is making significant inroads in the analyst's compendium of instrumentation available for the analysis of drugs in biological fluids, tissues, and other specimens of interest. LC/MS(/MS) has the unique capability of analyzing substances frequently not analyzable by any other means. Furthermore, LC/MS(/MS), particularly LC/MS/MS instrumentation, has shown a precipitous drop in cost, making it more accessible to the smaller laboratories. As such, an increasing number of methods for the analysis of drugs of abuse have been published using LC/MS(/MS) - in particular, those methods associated with LC/MS/MS. However, these methods are not without certain endemic problems/limitations such as ion source selection, matrix effects, endogenous interferences, and interlibrary matching of spectra. This review seeks to show what progress is being made to circumvent the perceived limitations of LC/MS(/MS). It presents methodologies for selected drugs of abuse (opioids, benzodiazepines, cannabinoids, cocaine, and the amphetamines) that have been developed in recent years for analysis in blood, urine, hair, and oral fluids, as well as certain other specimens. Emphasis is primarily directed toward those methodologies that have been developed recently for LC/MS/MS, but LC/MS methods are also addressed where appropriate., (Copyright © 2008 Central Police University.)

A distinct body of literature supports the association between clinical postures of the dental practitioner and work-related musculoskeletal disorders (WRMD). Several aids or devices have been tested to improve clinical posture in the interest of decreasing WRMD. The use of magnification lenses while performing dental procedures may increase the quality of work and decrease the likelihood of musculoskeletal problems. To date, only anecdotal and personal opinions had existed regarding the benefits of using magnification lenses, and no empirical evidence had authenticated the contention that use of magnification lenses exerts a positive change in operator posture. The objective of this study was to assess the effect magnification lenses had on the posture of dental hygiene students. Using a randomized crossover design, researchers videotaped nineteen senior dental hygiene students performing an intra-oral procedure with and without the use of magnification lenses. The tapes were then evaluated by a panel of five dental hygiene educators calibrated in the use of Branson's Posture Assessment Instrument (PAI). Results of a paired t-test indicate that the posture of the students while wearing magnification lenses was more acceptable (p=.019) than when wearing traditional safety glasses. Results of this study indicate a quantifiable change in acceptability of posture for clinicians wearing magnification lenses and suggest that the use of such lenses in dental education may be warranted.

Background: It has been speculated that periodontal probes can transmit periodontal pathogens from site to site. The purpose of this study was to evaluate the potential for bacterial transmission as a function of periodontal probe design., Methods: Four different periodontal probes were used to measure probing depths ranging from 0 to 3 mm and > or = 4 mm. Following measurement of each pocket, probes were transported to a laboratory and cultured on blood agar, and colony forming units (CFUs) were determined for total aerobic, anaerobic, and dark-pigmented colonies (DPCs). Eight randomly selected probe tips, representing each probe type and probing depth category, were selected for examination by scanning electron microscopy (SEM) to determine distribution and morphotypes of adhering microbes., Results: Results showed no statistically significant main effect for probes with respect to CFUs. However, there was a statistically significant increase in CFUs for deeper pockets when compared to pockets 0 to 3 mm. SEM observations were consistent among groups, regardless of probe design or probing depth. All probes exhibited a rough surface texture. Microbes were observed as single organisms or in aggregates and were adherent along the entire length of the probe up to the maximum probing depth., Conclusions: There was no difference in CFUs obtained as a function of periodontal probes. The rough surfaces of the probes used in this study likely promoted bacterial adherence through two different mechanisms: through scraping of the pocket walls by the roughened surfaces of the probe and by the high surface-free energy of the metal probes, facilitating bacterial adherence.

The purpose of this study was to examine by transmission (TEM) and scanning electron microscopy (SEM) the supragingival microbial plaque overlying the ulcerated gingival papillae of necrotizing ulcerative periodontitis (NUP) lesions in HIV-seropositive patients. The microbiota of NUP and HIV-seropositive patients with periodontitis has been reported to be similar to that of conventional periodontitis in non-infected subjects, although several investigators have also reported high recovery rates of microbes not generally associated with the indigenous oral microbial flora. Light and electron microscopic observations and microbial culture studies indicate a similar high prevalence of spirochetes in both necrotizing ulcerative gingivitis (NUG) and NUP. In addition, several studies have reported more frequent isolation of Candida albicans from diseased periodontal sites in HIV-seropositive patients than from non-diseased sites. Ten male and six female patients, each HIV-seropositive and exhibiting NUP, constituted the study population. Two biopsies of involved gingival papillae from between posterior teeth were obtained from each patient and processed for examination by both TEM and SEM. Microscopic examination revealed a surface biofilm comprised of a mixed microbial flora of various morphotypes in 81.3% of biopsy specimens. The subsurface flora featured dense aggregations of spirochetes in 87.5% of specimens. Zones of aggregated polymorphonuclear leukocytes and necrotic cells were also noted. Yeasts were observed in 65.6% of specimens and herpes-like viruses in 56.5% of the specimens. Collectively, except for the presence of yeast and viruses, the results suggest that the microbial flora and possibly the soft tissue lesions of NUP and necrotizing ulcerative gingivitis are very similar.

A series of novel phenolic compounds has been discovered as potent inhibitors of TNF-alpha-inducible expression of vascular cell adhesion molecule-1 (VCAM-1) with concurrent antioxidant and lipid-modulating properties. Optimization of these multifunctional agents led to the identification of 3a (AGI-1067) as a clinical candidate with demonstrated efficacies in animal models of atherosclerosis and hyperlipidemia.

A series of nitrobenzene compounds has been discovered as potent inhibitors of VCAM-1 expression and, therefore, potential drug candidates for autoimmune and allergic inflammatory diseases. Structure-activity relationship (SAR) studies showed that a nitro group and two other electron-withdrawing groups are essential for these compounds to be potent inhibitors of VCAM-1 expression.

Procedures used for the complete enzymic hydrolysis of proteins are reviewed. The successful application of complete enzymic hydrolysis in the detection of naturally occurring isopeptide crosslinks and various other types of chemically introduced crosslinks is described. The method may fail if the level of crosslinking is too high, or if crosslinking is accompanied by racemization. Although it is usual to cleave disulphide crosslinks prior to enzymic digestion, the necessity for this in all cases is questioned.

Aqueous solutions of the four tryptophan peptides, Ala-Trp-Val, Val-Trp-Ala, Ala-Ala-Trp-Val and Ala-Gly-Trp-Leu, have been irradiated with the light of wavelength greater than 295 nm. The major changes were destruction of the tryptophan residue, liberation of ammonia and the formation of photoproducts of increased molecular weight. Up to 40% of Ala-Ala-Trp-Val and Ala-Gly-Trp-Leu were converted to products with molecular weights ranging from two to four times those of the original tetrapeptides. Most of the yellow material formed during irradiation in air was present in the high molecular weight fractions. Irradiation of Ala-Gly-[14C]Trp-Leu gave the following identifiable photoproducts: Ala-Gly-Asp-Leu, Ala-Gly-(N'formyl)Kyn-Leu, Ala-Gly-Oia-Leu, and ammonia, where Kyn means kynurenine and Oia, beta-(3-oxindolyl)alanine.