Determination of specific and non-specific protein-protein interactions for beta-lactoglobulin by analytical ultracentrifugation and membrane osmometry experiments.

Protein-protein interactions are essential for the understanding of biological processes. Specific protein aggregation is an important aspect for many biological systems. In particular, electrostatic interactions play the key role for protein-protein interactions, as many amino acids have pH-dependent charge states. Moreover, protein dissociation is directly related to the solution pH, ionic strength, temperature and protein concentration. The subtle interplay between different specific and non-specific interactions is demonstrated for beta-lactoglobulin (BLG) with a focus on low salt concentrations, thus mimicking technically relevant processing conditions. BLG is a well-characterized model system, proven to attain its monomer-dimer equilibrium strongly dependent upon the pH of the solution. In this manuscript, we present a unique combination of analytical ultracentrifugation and membrane osmometry experiments, which quantifies specific and non-specific interactions, i.e. in terms of the dimer dissociation constants and the second osmotic virial coefficient, at pH 3 and 7 and sodium chloride concentrations of 10 mM and 100 mM. This provides direct insight to protein-protein interactions for a system with a concentration-dependent monomer-dimer equilibrium. Moreover, using a coarse-grained extended DLVO model in combination with molecular dynamics simulations, we quantify non-specific monomer-monomer, monomer-dimer and dimer-dimer interactions as well as the binding free energy of BLG dimerization from theoretical calculations. The experimentally determined interactions are shown to be mainly governed by electrostatic interactions and further agree with free energy calculations. Our experimental protocol aims to determine non-specific and specific interactions for a dynamically interacting system and provides an understanding of protein-protein interactions for BLG at low salt concentrations.

Molecular weight dependent structure of the exopolysaccharide levan.

Levan is a bacterial homopolysaccharide, which consists of ß-2➔6 linked ß-(D)-fructose monomers. Because of its structural properties and its health promoting effects, levan is a promising functional ingredient for food, cosmetic and pharmaceutical products. The properties of levan have been reported to be linked to its molecular weight. For a better understanding of how the molecular weight determines its polymer conformation in aqueous solution, levan produced by the food grade acetic acid bacterium Gluconobacter albidus TMW 2.1191 was analysed over a broad molecular weight range using dynamic and static light scattering and viscometry. Low molecular weight levan exhibit a compact random coil structure. As the molecular weight increases, the structure transforms into a compact non-drained sphere. The density of the sphere continues to increase with increasing molecular weight. This resulted in a negative exponent in the Mark-Houwink-Sakurada Plot. For the first time, an increase in molecular density with increasing molecular weight, as determined by a negative Mark-Houwink-Sakurada exponent, can be shown for biopolymers. Our results reveal the unique properties of high-molecular weight levan and confirm the need of further systematic studies on the structure-function relationship of levan for its targeted use in food, cosmetic and pharmaceutical applications.

Advance care planning in the palliative phase of people with intellectual disabilities: analysis of medical files and interviews.

BACKGROUND: Advance care planning (ACP) is a process in which professionals, patients and their relatives discuss wishes and options for future care. ACP in the palliative phase reduces the chance that decisions have to be taken suddenly and can therefore improve the quality of life and death. The primary aim of this study is to explore how ACP takes place in cases of people with intellectual disabilities (ID). METHOD: Medical files were analysed, and interviews were held in six care organisations for people with mild to severe ID. The data concerned people with ID (n = 30), 15 in the palliative phase, identified using the 'surprise question', and 15 who had died after an identifiable period of illness. Additional pre-structured telephone interviews were conducted with their relatives (n = 30) and professionals (n = 33). RESULTS: For half of the people with ID who had died, the first report in their file about palliative care (needs) was less than 1 month before their death. Professionals stated that ACP was started in response to the person's deteriorating health situation. A do-not-attempt-resuscitation order was recorded for nearly all people with ID (93%). A smaller group also had other agreements between professionals and relatives documented in their files, mainly about potentially life-sustaining treatments (43%) and/or hospitalisation admissions (47%). Relatives and professionals are satisfied with the mutual cooperation in ACP in the palliative phase. Cognitive and communication disabilities were most frequently mentioned by relatives and professionals as reasons for not involving people with ID in ACP. CONCLUSIONS: Advance care planning in the palliative phase of people with ID focuses mainly on medical issues at the end of life. Specific challenges concern a proactive identification of changing needs, fear to initiate ACP discussions, documentation of ACP in medical files and the involvement of people with ID in ACP. It is recommended that relatives and professionals should be informed about the content of ACP and professionals should be trained in communicating in advance about wishes for future care.

Do-Not-Attempt-Resuscitation orders for people with intellectual disabilities: dilemmas and uncertainties for ID physicians and trainees. The importance of the deliberation process.

BACKGROUND: Not much is known about Do-Not-Attempt-Resuscitation (DNAR) decision-making for people with intellectual disabilities (IDs). The aim of this study was to clarify the problems and pitfalls of non-emergency DNAR decision-making for people with IDs, from the perspective of ID physicians. METHODS: This qualitative study was based on semi-structured individual interviews, focus group interviews and an expert meeting, all recorded digitally and transcribed verbatim. Forty ID physicians and trainees were interviewed about problems, pitfalls and dilemmas of DNAR decision-making for people with IDs in the Netherlands. Data were analysed using Grounded Theory procedures. RESULTS: The core category identified was 'Patient-related considerations when issuing DNAR orders'. Within this category, medical considerations were the main contributory factor for the ID physicians. Evaluation of quality of life was left to the relatives and was sometimes a cause of conflicts between physicians and relatives. The category of 'The decision-maker role' was as important as that of 'The decision procedure in an organisational context'. The procedure of issuing a non-emergency DNAR order and the embedding of this procedure in the health care organisation were important for the ID physicians. CONCLUSION: The theory we developed clarifies that DNAR decision-making for people with IDs is complex and causes uncertainties. This theory offers a sound basis for training courses for physicians to deal with uncertainties regarding DNAR decision-making, as well as a method for advance care planning. Health care organisations are strongly advised to implement a procedure regarding DNAR decision-making.

'To move or not to move': a national survey among professionals on beliefs and considerations about the place of end-of-life care for people with intellectual disabilities.

BACKGROUND: The aim of this article was to investigate the beliefs and considerations of professionals concerning an appropriate environment for end-of-life care for people with intellectual disabilities (ID). METHOD: A survey questionnaire was composed based on a scan of relevant literature and the results of group interviews with professionals, family members and people with ID. The questionnaire focused on the respondents' general beliefs about an appropriate environment for end-of-life care and their specific considerations regarding the place of care of the last client for whom the respondent provided end-of-life care. The questionnaire was sent to 294 care staff members recruited from a nationally representative panel of nurses and social workers, 273 ID physicians recruited from the members list of the Dutch professional association of ID physicians, and 1000 general practitioners (GPs) recruited from a nationally representative sample from a national registration of GPs. RESULTS: The overall response was 46%. Professionals predominantly believe that all efforts should be made to ensure that a person with ID receives end-of-life care in their own home environment, and that 24/7 care is available. Respondents indicated that most of the clients (79%) who had last received end-of-life care from an ID care service were able to stay in their own home environment. Decisions to keep the client in their own home environment were primarily based on the familiarity of the environment and the expertise of the team in end-of-life care. Insufficient expertise and a lack of adequate equipment were the main considerations in decisions to move a client. Despite the belief of care staff in particular that the wishes of the person with ID should always be leading when deciding on the place of end-of-life care, only 8% of the care staff and ID physicians explicitly mentioned that the client's wishes were taken into account in actual decision-making. CONCLUSIONS: Professionals agree that end-of-life care for people with ID should preferably take place in the client's home environment, even when nursing expertise, experience and adequate equipment are not (yet) in place. Nonetheless, a lack of expertise in end-of-life care is the foremost consideration in decisions to move a client. If ID care services want to promote end-of-life care in the client's own home, we recommend formulating a policy on how to realise end-of-life care in the client's own home environment and provide sufficient training and support for staff. To involve people with ID as much as possible, we recommend that professionals integrate more collaborative principles in decision-making about the place of end-of-life care.

Wolf-Hirschhorn (4p-)syndrome in a near adult with major depression; successful treatment with citalopram.

The Wolf-Hirschhorn Syndrome (WHS) or 4p-deletion syndrome is characterized by mental retardation, growth retardation, microcephaly and typical facial features. In addition, a wide spectrum of somatic abnormalities can be associated that may cause comorbidity. The syndrome has been extensively described in children, but less information is available about adult patienis. In this case report a near adult female WHS patient is described who developed a major depression with atypical symptoms that was successfully treated with citalopram. Treatment for one year in the effective dose prevented recurrence of depressive symptomatology.

Osteoporosis and intellectual disability: is there any relation?

One of the causes of osteoporosis is immobility. The present study examined osteoporosis in 23 bedridden adults with intellectual disability. It was found that the bone mineral density of the subjects was low, even though their calcium intake was more than adequate. Vertebral and other fractures were concentrated mainly in the elderly subjects (> 50 years). Very low vitamin D levels were also found in the subjects despite good nutritional levels. It is concluded that people with intellectual disability and mobility disorders are at risk of metabolic bone disease.