Management of Adult Traumatic Brachial Plexus Injury.

Brachial plexus injury is not uncommon in our country like Bangladesh and it causes functional damage and physical disability of the upper limbs. Most of the cases were caused by motor vehicle accident. We have conducted a prospective study for the operative treatment of 105 adult traumatic brachial plexus injury cases in Hand unit in the department of Orthopaedics, Bangabandhu Sheikh Mujib Medial University (BSMMU) during January 2012 to July 2019. The main surgical options for brachial plexus injury include primary reconstructive surgery such as neurolysis, direct repair, nerve graft, nerve transfer (neurotization) and possibly free functioning (gracilis) muscle transfer and secondary reconstructive procedure such as tendon transfer, arthrodesis, FFMT and bony procedure. Each of these procedures is used either alone or in combination for particular clinical scenarios. Aims and objectives of this study was to restoration of shoulder abduction and external rotation, elbow flexion and hand function are goal of treatment of adult traumatic brachial plexus injury. Age range was from 14 years to 55 years (mean age 26 years). Male were 95 and female were 10 cases. Time from trauma to surgery was valid 3 months to 9 months. Motor cycle accident was most common mechanism of injury. Upper plexus (C5, C6) injury was 52 cases, extended upper plexus (C5, C6 & C7) injury was 19 cases and global brachial plexus injury was 34 cases. When there is high suspicion of root avulsions, early exploration and reconstruction is indicated. Operate these patients 2-3 months after their injury. In other patients without high suspicion of root avulsion, we routinely perform exploration between 3 to 6 months after injury when no adequate sign of recovery are present. Common reconstructive options are any injury with neuroma in continuity with conductive nerve action potential (NAP): only neurolysis or any injury with nerve rupture or postganglionic neuroma not conducting nerve Action potential (NAP) and good proximal nerve: Direct repair or repair with nerve graft or nerve transfer if possible. Follow up period from 6 months to 6 years. The best results were obtained in C5, C6 and C5, C6 & C7 brachial plexus injury cases. SAN to SSN, Oberlin II and long head triceps motor branch to anterior division of axillary nerve transfer for C5 & C6 injury or upper plexus injury and in addition intercostals nerve to anterior division of axillary nerve and AIN branch of median nerve to ECRB for C5, C6 & C7 (extended upper plexus injury). Extra-plexus and intra-plexus neurotization was done in global brachial plexus injury cases and 5 cases by contra-lateral C7 to median nerve by vascularised ulnar nerve graft and only 2 cases contra-lateral C7 to lower trunk through pre spinal or pre tracheal route were done and only one case by FFMT. Few cases gain shoulder abduction and elbow flexion but no improvement of hand function and most cases even by FFMT still in follow up. Results of surgical treatment of upper and extended upper brachial plexus injury cases were satisfactory on the other hand recovery of shoulder abduction and elbow flexion was acceptable and comparable to other study in global brachial plexus injury and recovery of hand function were poor.

Management of the Hand Tumors.

Tumors in the hand are relatively uncommon but 95% are benign. Tumors occurring in the hand, forearm and arm often have unique growth patterns and potential for metastasis that may be different from those seen elsewhere in the body. Secondary metastatic tumors in the hand are very rare (0.1%). Diagnosis is mainly clinical, but X-ray, USG and MRI help as a diagnostic aid. The aim of the study was to early diagnosis, see the pattern and proper management of the hand tumor and ensure good hand function. This prospective study was done from January 2004 to July 2019. We found 220 hand tumors in the hand unit, Department of Orthopaedic Surgery, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka Bangladesh. Among 220 patients, male were 114(51.81%) and female were 106 (48.19%). Out of 220 patients we found 190(86.36%) benign tumor and tumor like lesions and 30(13.64%) was malignant hand tumors. Out of 190 benign lesions, benign tumor was 158(83.15%) and 32(16.85%) was tumor like lesions. Among 158 benign tumor, bone tumors were 40(25.31%) and soft tissue tumours were 138(74.69%). Out of soft tissue tumor, peripheral nerve tumor was 20(12.66%). Enchondroma and Giant cell tumors are the most common among the benign bone tumors, on the other hand giant cell tumors of tendon sheath, Glomus tumor, haemangioma, neurofibroma, schwanoma are the common soft tissue tumors. Compound palmar ganglion, fibromatosis and tuberculosis of phalanx are the most common tumor like lesions. Synovial sarcoma 10(33.33%), osteosarcoma 03(10%), chondrosarcoma 03(10%), ewings sarcoma 02(6.66%), fibrosarcoma 04 (13.33%), Malignant fibrous histocytoma 01(3.33%), soft tissue sarcoma 01(3.33%), Merkel cell tumor 01(3.33%), pleomorphic Rabdomyosarcoma 01(3.33%), malignant melanoma 01(3.33%), clear cell sarcoma of tendon and aponeurosis 01(3.33%), undifferentiated carcinoma 01(3.33%) and extra skeletal chondro sarcoma 01(3.33%) were the malignant tumors. Most of the benign lesions recovered fully after excision except neurofibroma and malignant tumors were treated with excision (including amputation) and chemo-radiotherapy successfully, but 4 patients were refereed to higher center due to recurrence and deteriation of hand function and one patient died due to metastasis. Malignant hand tumor management is very difficult even after amputation with multidisciplinary approach. Hand tumor is uncommon and malignant tumors are rare but any abnormal lump or bump in the hand or wrist is considered as tumor. Early detection and intervention are essential for better prognosis and survival for malignant tumors of hands and upper limbs.

Management of Avascular Necrosis (AVN) of Femoral Head by Core Decompression with Tensor Fascia Lata (TFL) Muscle Pedicle Bone Graft.

Avascular necrosis (AVN) of femoral head is an increasingly common cause of musculoskeletal disability. Most of the cases caused by steroid induced and traumatic but idiopathic cause are not also uncommon. Almost all the patients presented with pain at the hip, limping gait, restricted movement and difficulty in waking and squatting and becomes disabled. Core decompression and muscle pedicle bone graft at stage IIA, IIB and III provides painless and mobile life. Core decompression supplemented with bone graft to enhance mechanical support and augment healing. We have started a prospective study for the treatment of AVN of Femoral head at stage IIA, IIB and III by core decompression and Tensor fascia lata muscle pedicle bone graft in the department of Orthopaedic surgery Bangabandhu Seikh Mujib Medical University (BSMMU), Dhaka, Bangladesh from January 2009 to December 2019. Aim of the study was to assess the effectiveness of core decompression and tensor fascia lata muscle pedicle bone graft in the treatment of AVN of femoral head at stage IIA, IIB and III. A total 48 patients and 65 hips were operated. Out of 48 patients, male was 30(62.50%) and female was 18(37.5%). Male-Female ratio was 1.66:1. Age of the patients ranging from 20 years to 50 years, mean age 36±4.65 years. According to aetiology corticosteroid induced was 47/65 (72.31%), idiopathic was 8(12.31%), post traumatic was 4(6.15%), ITP was 2(3.08%), ALL was 2(3.08%), and alcohol induced was 2(3.08%) of femoral head involvement. According to Ficat and Arlet's staging, stage IIA hip involvement was 28/65(43.08%), stage IIB was 32(49.23%) and stage III was 5(07.69%). All patients were treated with core decompression along with tensor fascia lata (TFL) muscle pedicle bone graft. All patients were followed clinically and radiologically at regular interval. Follow up period was 6 months to 10 years. Harris hip score (HHS) was used for evaluation of clinical outcome. Among the 65 hips, 24(36.92%) was excellent outcome (HHS >90), 30(46.15%) was good outcome (HHS: 80-90), 7(10.78%) was fair outcome (HHS: 70-79) and 4(6.15%) was poor outcome. For valid statistical analysis excellent and good results were grouped as satisfactory that was 54(83.07%) and fair and poor results were grouped as unsatisfactory that was11(16.93%), p value is <0.001 that is significant. It has been concluded that core decompression and TFL muscle pedicle bone graft is a pain relieving, head preserving procedure and improve hip function for the management of AVN of femoral head in stage IIA, IIB and III.

Limb Salvage by Resection Arthrodesis with the use of Osteoarticular Allograft in the Treatment of Aggressive Giant Cell Tumour around the Knee.

Osteoarticular allografts have provided the chance of limb-sparing trial in tumor surgery. Several authors have reported 50-75% long term (>10 years) successful use of these types of grafts, and large well recognized series provide confirmation that limb reconstruction following extensive resection of bone and joints has been possible with their use. Infection has been a major problem, affecting up to 12 per cent of recipients and often resulting in re-operations and infrequently amputations. This prospective Interventional study was conducted in the Department of Orthopaedic Surgery, Bangabandhu Sheikh Mujib Medical University (BSMMU) and Biomedical Research division, Atomic Energy Centre, Savar, Dhaka, Bangladesh from January 2008 to December 2017. In this study patients' age were 20-50 years and male was 12(60%) & female was 8(40%). We assessed the results of 20 limb-salvage procedures (Resection-Arthrodesis Procedure) using 11-18cm of distal femur or proximal tibial osteoarticular allografts after wide resection of aggressive or malignant Giant Cell Tumour (GCT) around the knee joint, Campanacci Grade III or recurrent case of Campanacci Grade II. At the ten-year follow-up, two patients had died, one due to infection and tumor metastasis to the lungs and one due to medical causes. The allografts survived for more than five years was twelve patients (60%) all of whom had good function, ranging from 73% to 90% of normal. The allografts were removed because of fracture in two patients and infection in two patients. Remaining three patients allograft was survived with satisfactory function but follow up was 3 years. All postoperative problems related to the allograft reconstruction were documented. Functional outcome was evaluated using the Musculoskeletal Tumour Society Scoring System and at least more than 3 years follow up should be taken for categorization of the results. Among the 20 patients, satisfactory result was 15(75%) patients and unsatisfactory result was 5(25%) patients. P value was <0.001.

Interaction of Cu+2 with α-Crystallin: A Biophysical and Mass Spectrometric Study.

BACKGROUND: αA- and αB- crystallin are members of small heat shock protein family with chaperone property. Their interactions with Cu2+ ions are reported in neurodegenerative diseases. We have been studying the effect of small ionic molecules on the stability of α-crystallin. Cu2+ is co-ordinated with αB-crystallin involving three histidine residues and one aspartic acid residue as potential binding sites. However, copper binding sites for the oligomeric native protein αA-crystallin protein is not known. OBJECTIVE: The objective of this study was to study oligomerization and stability of αA- and αBcrystallin in presence and absence of Cu2+ ions and to find binding sites of Cu2+ on αA-crystallin. METHODS: The recombinant Human αA- and αB-crystallin proteins were purified after overexpression from the E. coli BL21DE3 cell lysate by a combination of ion-exchange and gel filtration chromatography. Mass analysis of αA- and αB-crystallin in absence and presence of Cu2+ were carried out by MALDI TOF MS. Stability of αA-crystallin in presence and absence of Cu2+ was determined by equilibrium urea denaturation experiments. The equilibrium urea unfolding profiles of the αA-crystallin in absence and presence of different Cu2+ concentrations were fitted according to the three state model of protein unfolding. Dynamic Light Scattering (DLS) measurements were carried out to detect the oligomeric size of αA-crystallin in presence and absence of Cu2+ during urea unfolding. Histidine residues were modified by DEPC (Diethyl pyro carbonate). Chemically modified and unmodified αA-crystallin was digested by trypsin prior to MALDI MS analysis. Cu2+ pre-incubation was done before the chemical modification. RESULTS: Mass spectrometric detection of intact protein allows direct measurement of Cu2+ ions bound to the protein. Thus the average numbers of Cu2+ bound to αA- and αB-crystallin were 4.2 and 3.6 respectively per subunit. It is seen that in presence of Cu2+ ions the free energy (ΔG) of unfolding of αA-crystallin almost doubled. The size analysis by dynamic light scattering data clearly indicated that in presence of Cu2+ ions the oligomeric size remain unchanged with increasing urea solutions. Mass spectrometric detection with chemical modification of histidine residues of αA-crystallin in presence and absence of Cu2+ indicated that amino acid residues H107, H100, H115 of αA-crystallin are involved in Cu2+ binding. CONCLUSION: Our results indicated that Cu2+ helped in increasing stability of αA-crystallin and three histidine residues H100, H107 and H115 of αA-crystallin are Cu2+ binding residues.

Assessing the Rehabilitation of Achilles Tendon Ruptures using Modified Teuffer and Lindholm Technique.

The aim of this study is to assess the optimum rehabilitation and the functional outcome of open repaired Achilles tendon ruptures. This study was conducted for the 18 consecutive patients of complete ruptures at Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh from 2012 to 2013. Two groups were considered during 6 to 18 months post-operative observation and each group consist 9 patients. In the Group I, modified Teuffer's and in Group II, Lindholm operative methods were employed for the open repair of Achille tendon. The post operative outcomes were assessed for both of the groups through the modified Thermann's scores. In this study the patients median age was seen 39 years with 72.2% male and 27.8% female. The Thompson test was found positive in pre-operative and negative in post-operative outcome. The results shown that Achilles tendon ruptures occurred in 4 to 6cm rupture site, where the rupture side was 61.1% left and 38.9% right. The subjective overall assessment of total Thermann's scores were found very good (91 to 96) in 4 cases and (90 to 98) in 3 cases for Group I and Group II, respectively. Both of the operative techniques were found accountable results for rehabilitation. Therefore, based on the further statistical evidence of higher correlations and errors it may be concluded that Achilles tendon ruptures can be treated by modified Teuffer's or Lindholm technique.

Close Intramedullary Interlocking Nailing Versus Locking Compression Plating In the Treatment of Closed Fracture Shaft of the Tibia.

Fracture of tibial shaft is the commonest site of long bone fractures due to its superficial location involving young or middle-age people. Proper management is an important issue regarding the future effective movements. In this study patients were grouped in closed Intra medullary interlocking nailing and locking compression plating. Post-operative follow up at 2 weeks, 6 weeks, 12 weeks and 3 months thereafter up to 6 months were done. Each of the patients was evaluated clinically and radiologically by tucker criteria of Tuker et al. Patients were assessed for pain on full weight bearing and kneeling, shortening and range of motion of knee and ankle joints. Radiological assessment for union of fracture, alignment of fracture and angulations and position of nail and screws and infection were observed during follow up. A total number of 32 patients were selected but only 27 patients were available for follow up for a period of 6 months. They were grouped into Group A, consisting of 15 patients who took the treatment in the form of closed intramedullary interlocking nailing and Group B, consisting of 12 patients those underwent ORIF with locking compression plating. In both of the groups Motor Vehicle Accident was the main mechanism of trauma. Fracture involving the middle 3rd of the tibia is common in both the groups. During post-operative follow up, four patients in Group A complained anterior knee pain, one patient in Group B had superficial infection, most of the patients had no restriction of movement in the ankle and knee joints and a single patient in Group B showed 1.5cm shortening of the lower limb. Period of hospital stay and fracture union time were less in Group A, which was statistically significant. Both groups showed excellent result with minimum complications. So this study permits to conclude that close IM interlocking nailing and open reduction and internal fixation by locking compression plating is equally effective for the management of close fracture shaft of the tibia.

Interaction of α-crystallin with some small molecules and its effect on its structure and function.

BACKGROUND: α-Crystallin acts like a molecular chaperone by interacting with its substrate proteins and thus prevents their aggregation. It also interacts with various kinds of small molecules that affect its structure and function. SCOPE OF REVIEW: In this article we will present a review of work done with respect to the interaction of ATP, peptide generated from lens crystallin and other proteins and some bivalent metal ions with α-crystallin and discuss the role of these interactions on its structure and function and cataract formation. We will also discuss the interaction of some hydrophobic fluorescence probes and surface active agents with α-crystallin. MAJOR CONCLUSIONS: Small molecule interaction controls the structure and function of α-crystallin. ATP and Zn+2 stabilize its structure and enhance chaperone function. Therefore the depletion of these small molecules can be detrimental to maintenance of lens transparency. However, the accumulation of small peptides due to protease activity in the lens can also be harmful as the interaction of these peptides with α-crystallin and other crystallin proteins in the lens promotes aggregation and loss of lens transparency. The use of hydrophobic probe has led to a wealth of information regarding the location of substrate binding site and nature of chaperone-substrate interaction. Interaction of surface active agents with α-crystallin has helped us to understand the structural stability and oligomeric dissociation in α-crystallin. GENERAL SIGNIFICANCE: These interactions are very helpful in understanding the mechanistic details of the structural changes and chaperone function of α-crystallin. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

Evaluation of outcome of surgical excision of the nidus of osteoid osteoma of long bone.

Osteoid osteoma is a benign bone tumour usually found in the lower extremities of children and young adults. This tiny bone tumour causes pain out of all proportion to its size and hinders the daily activities. This Quasi-experimental study conducted in the department of Orthopaedic surgery of BSMMU from January 2008 to December 2009. Twenty one patients were included in the study where purposive sampling technique was used on the basis of inclusion and exclusion criteria and all the ethical conditions were fulfilled. Diagnosis was almost obtained by taking history, clinical examination, and relevant investigations. Clinical variables were age, sex, site, pain, swelling, deformity and outcome variables were painless active life, removal of swelling, prevention of deformity, rate of recurrence. After localization of the tumour with the help of C arm, the nidus was excised in a small block of bone. The outcome is categorized by consensus, as clinically successful, only if the patient was free of pain and was taking no medication. The treatment was considered to have failed if a subsequent procedure had been performed to remove tumour. Among 21 cases, 14(66.7%) were male and 7(33.7%) were female. Maximum number of patients 15(71.4%) was between 10 years to 20 years. Most of the patients (76.2%) affected by osteoid osteoma were young students and most of the patients (95.2%) experienced moderate aching pain, usually aggravating at night which was typically relieved by aspirin or other NSAIDs (71.4%). Lower limbs (76.2%) particularly femur and tibia were commonly affected. Out of 21 patients, 19(90.5%) patients have got immediate pain relief or required no medication. In only 2 patients (9.5%), subsequent procedure has been performed to relief pain. So, successful outcome (in 19 out of 21) was significantly (p<0.001) higher in comparison to failed. Surgical excision of the nidus is a simple and easy procedure and does not require extensive resection of bone. If localization is done properly success rate is high and patients can return to normal daily activities.

Management of unicameral bone cyst by using freeze dried radiation sterilized bone allograft impregnate with autogenous bone marrow.

Unicameral bone cyst is a common benign bone tumor and most frequent cause of the pathological fracture in children. We have started a prospective study for that treatment of unicameral bone cyst by using freeze dried radiation sterilized bone allograft impregnated with autogenous bone marrow in the department of Orthopaedics, Bangabandhu Sheikh Mujib Medical University (BSMMU) during May 1999 to April 2012. Aim of this study was to see Freeze dried radiation sterilized bone allograft impregnate with autogenous bone marrow a satisfactory graft material in the treatment of unicameral bone cyst as well as factors such as patients age, sex, cyst size and site of lesion influence on cyst healing. A total 35 patients of unicameral bone cyst were operated. In this study out of 35 patients, male were 22(62.86%) and female were 13(37.14). Male Female ratio 22:13(1.70:1) Age of the patients ranging from 2 years 6 month to 20 years, mean age 12.18 years more common 11 years to 20 years 29(82.86%) patients. Common bones sites involvements are proximal end of Humerus 20(57.14%), proximal end of Femur 7(20 %), proximal end of Tibia 3(8.57%), Calcanium 2(5.71%), proximal end of Ulna 1(2.86%), shaft of Radius 1(2.86%) and Phalanx 1(2.86%). Final clinical outcome of unicameral bone cyst treated by thorough curettage of cavity and tightly filled with freeze dried radiation sterilized bone allograft impregnate with autogenous bone marrow in which healed (success rate) 88.57% (31) and recurrence rate is 11.43% (4). P value is <0.001. Follow up period was 6 month to 11 years. From our study it was realized that freeze dried radiation sterilized bone allograft impregnated with autogenous bone marrow is useful graft material for healing of the lesional area as well as restoring structural integrity for the treatment of unicameral bone cyst.

Outcome of early active mobilization in flexor tendon repair in zone II in hand.

Early controlled motion programs after flexor tendon repair in zone II of hand are designed to minimize adhesion formation by promoting the excursion of repaired tendons. The flexor tendon surgery especially in zone II is complicated. It is simplest in the newly injured and unscarred digit and the results of correctly rehabilitated primary repair are likely to be the best attainable. We conducted a study including 18 patients with 52 digits involving 80 flexor tendons in zone II to observe and record the result of the primary or delayed primary repair with early active mobilization protocol. Thirteen (72.22%) patients were below 30 years of age. Sixteen cases (88.89%) were sustained injury by sharp instrument either accidentally or by assault. Ring and little finger were involved in 50% instances. The repair was done with the modified Kessler core suture technique with locking epitendinous sutures with a knot inside the repair site, using polypropylene 4-0 and 6-0 sutures. The final assessment was done at 6 months post repair using the Louisville system of Lister et al. 61.54% (n=32) digits were shown excellent result whereas good results were seen in 23% (n=12) digits. Fair was shown 7.69% (n=4) digits and 7.69% (n=4) digits were shown poor results. P value was <0.001 by Z test which is significant. Complications included tendon rupture in 3(5.77%) cases (one thumb, one ring and one little finger) and contracture in 4(7.69%) cases whereas superficial infection and flap necrosis was seen in one (1.92%) case each. The primary or delayed primary repair of cut flexor tendons in zone II using the modified Kessler core suture and epitendinous suture with early active mobilization protocol has been given good result, with minimal complications.

Structure and functional properties of a multimeric protein αA-Crystallin adsorbed on silver nanoparticle surface.

Proteins adsorb onto a nanoparticle surface to form a protein-nanoparticle corona which becomes the identity of the nanoparticle in the cellular environment. Conformation of the protein at the interface influences the cellular uptake of the nanoparticle. Hence, interaction of proteins with nanomaterials is of special significance in the field of biotechnology. Adsorption of protein on the nanoparticle surface is a complex process that depends on the dielectric properties and pH of the medium, surface morphology and surface heterogeneity of the nanoparticle, and the quaternary structure of the protein. Thus, interaction of a large multimeric protein with a nanoparticle will be different from that of small oligomeric proteins. In this article we report the conformational and functional properties of a large oligomeric protein αA-Crystallin, a major constituent of the mammalian eye lens, adsorbed onto silver nanoparticle surface. Selective alkylation of the two cysteine residues at the α-Crystallin domain, followed by ITC study showed that these residues play crucial roles in the interaction process. The chaperone function and the refolding capacity of the protein, which is primarily governed by the α-Crystallin domain, are lost to a significant extent when adsorbed onto AgNP surface. The protein in the interface also shows loss of oligomerization that is linked to the biological activity of the protein. Nonetheless, the protein at bio-nano interface shows resistance to urea unfolding process as compared to protein in the solution phase. This might be due to the coordination of AgNP with two cysteine residues of ß8 and ß9 region of the α-Crystallin domain that imparts extra stability. The compactness in the structure of the adsorbed protein reduces the dynamics of the subunit exchange, which was confirmed by the FRET study. The secondary structure of αA-Crystallin bound to AgNP at substoichiometric ratio remained native-like.

Spectroscopic studies of the unfolding of a multimeric protein α-crystallin.

α-Crystallin is a multimeric eye lens protein having molecular chaperone-like function which is crucial for lens transparency. The stability and unfolding-refolding properties of α-crystallin plays important roles for its function. We undertook a multi probe based fluorescence spectroscopic approach to explore the changes in the various levels of organization of this protein at different urea concentration. Steady state fluorescence studies reveal that at 0.6M urea a compact structural intermediate is formed which has a native-like secondary structure with enhanced surface exposure of hydrophobic groups. At 2.8M urea the tertiary interactions are largely collapsed with partial collapse of secondary and quaternary structure. The surface solvation probed by picosecond time resolved fluorescence of acrylodan labeled α-crystallin revealed dry native-like core of α-crystallin at 0.6M urea compared to enhanced water penetration at 2.8M urea and extensive solvation at 6M urea. Activation energy for the subunit exchange decreased by 22 kJ mol(-1) on changing urea concentration from 0 to 0.6M compared with over 75 kJ mol(-1) on changing urea concentration from 0 to 2.8M. Light scattering and analytical ultracentrifugation techniques were used to determine size and oligomerization of the unfolding intermediates. The data indicated swelling but no oligomer breakdown at 0.6M urea. At 2.8M urea the oligomeric size is considerably reduced and a monomer is produced at 6M urea. The data clearly reveals that structural breakdown of α-crystallin does not follow hierarchical sequence as tertiary structure dissolution takes place before complete oligomeric dissociation.

Interaction of silver nanoparticles with proteins: a characteristic protein concentration dependent profile of SPR signal.

Silver nanoparticles are finding increasing applications in biological systems, for example as antimicrobial agents and potential candidates for control drug release systems. In all such applications, silver nanoparticles interact with proteins and other biomolecules. Hence, the study of such interactions is of considerable importance. While BSA has been extensively used as a model protein for the study of interaction with the silver nanoparticles, studies using other proteins are rather limited. The interaction of silver nanoparticles with light leads to collective oscillation of the conducting electrons giving rise to surface plasmon resonance (SPR). Here, we have studied the protein concentration dependence of the SPR band profiles for a number of proteins. We found that for all the proteins, with increase in concentration, the SPR band intensity initially decreased, reaching minima and then increased again leading to a characteristic "dip and rise" pattern. Minimum point of the pattern appeared to be related to the isoelectric point of the proteins. Detailed dynamic light scattering and transmission electron microscopy studies revealed that the consistency of SPR profile was dependent on the average particle size and state of association of the silver nanoparticles with the change in the protein concentration. Fluorescence spectroscopic studies showed the binding constants of the proteins with the silver nanoparticles were in the nano molar range with more than one nanoparticle binding to protein molecule. Structural studies demonstrate that protein retains its native-like structure on the nanoparticle surface unless the molar ratio of silver nanoparticles to protein exceeds 10. Our study reveals that nature of the protein concentration dependent profile of SPR signal is a general phenomena and mostly independent of the size and structure of the proteins.

Identification of histidine residues involved in Zn(2+) binding to αA- and αB-crystallin by chemical modification and MALDI TOF mass spectrometry.

α-Crystallin, a member of the small heat shock protein family is the major protein of mammalian eye lens and is a molecular chaperone. As there is no protein turn over in the lens, stability of α-crystallin is one of the most crucial factors for its survival and function. We previously reported that the molecular chaperone-like activity and stability of α-crystallin dramatically increased in the presence of Zn(2+) (Biochemistry, 2008). We also reported that each subunit of α-crystallin could bind multiple zinc ions through inter-subunit bridging giving rise to enhanced stability (Biopolymers, 2011). The amino acid residues involved in zinc binding were not known. Since cysteine residues were not responsible for binding to Zn(2+), we tried to identify the histidine residues bound to zinc ions. We modified recombinant αA- and αB-crystallin with diethylpyrocarbonate (DEPC) a histidine modifying reagent, in presence and absence of Zn(2+) followed by tryptic digestion. The residues modified by DEPC were identified through peptide mass matching by MALDI mass spectrometry. We have clearly identified H79, H107 and H115 of αA-crystallin and H104, H111 and H119 of αB-crystallin as the Zn(2+) binding residues. The significance of the histidine rich sequence region of α-crystallin for its stability is discussed.

Modulation of pathway of insulin fibrillation by a small molecule helix inducer 2,2,2-trifluoroethanol.

Many proteins form ordered irreversible structural aggregates called amyloid fibrils, which are associated with numerous neurodegenerative diseases. Insulin, a largely α-helical protein associated with type II diabetes, self-assembles to form amyloid fibrils in vitro. Insulin fibrillation goes through a number of intermediate phases that includes a soluble oligomeric phase believed to be the most toxic phase. Small molecules may play a very important role in modulating the fibrillation pathways. It is possible to induce and stabilize helix structures in proteins by a fluorinated alcohol 2,2,2-trifluoro ethanol (TFE). Since fibrillation process of many proteins is associated with conversion of α-helical structures into ß-sheet configuration, we thought it would be interesting to study the effect of TFE on the fibrillation of insulin. In absence of TFE, soluble protofibrillar oligomeric intermediates formed directly from the insulin trimer. The protofibrillar aggregates transformed into mature fibrils over time. We demonstrated that although TFE did not prevent the appearance of matured amyloid fibrils, it prevented the appearance of soluble aggregates of insulin. TFE converted the insulin trimer into monomers and fibril formation proceeded from the monomeric state in a cooperative way avoiding the soluble oligomeric phase. At 25% TFE, distinct morphological changes resulting in more discrete fibrils were visible. The effect of the small molecule TFE on the avoidance of the formation soluble oligomeric state during fibrillation may have considerable implications in reducing cellular toxicity.

Stabilization of oligomeric structure of α-crystallin by Zn+² through intersubunit bridging.

α-Crystallin, the major protein of mammalian eye lens, is a member of the small heat shock protein family and is a molecular chaperone. We previously reported that its molecular chaperone function as well as stability increased in presence of Zn+². Despite the effect of Zn+² on the structure and function of α-crystallin, evidence for direct interaction between them remained elusive. We now present the MALDI mass spectrometric data that shows direct evidence of Zn+² binding to recombinant αA- and αB-crystallin. The binding stoichiometry was over three Zn+² per subunit of α-crystallin at zinc/protein molar ratio of 20. Observation of multiple Zn+² binding is consistent with the large increase in thermodynamic stability. Sequence-based analysis of αA- and αB-crystallin predicted both proteins to be nonzinc binding proteins. Our dynamic light scattering data shows that Zn+² stabilizes the oligomeric structure of α-crystallin by bridging neighboring subunits in multiple centers. Despite the low affinity binding, the intersubunit bridging by multiple Zn+² makes the oligomer so stable that oligomer breakdown does not occur even at 6M urea. The subunit bridging has been supported by our FRET data that showed absence of subunit exchange in presence of zinc. MALDI data also showed that the interaction of α-crystallin with Zn+² is quite different from other bivalent metal ions. Bound Zn+² could be easily removed by dialysis of the complex. The relevance of such weak interaction on the stability of the oligomeric structure of α-crystallin and its function in the eye lens has been discussed.

Effect of methylglyoxal modification of human α-crystallin on the structure, stability and chaperone function.

α-Crystallin functions as a molecular chaperone and maintains transparency of eye lens by protecting other lens-proteins. Non-enzymatic glycation of α-crystallin by methylglyoxal, plays a crucial role on its chaperone function and structural stability. Our studies showed that methylglyoxal modification even in lower concentration caused significant decrease in chaperone function of α-crystallin as reflected both in thermal aggregation assay and enzyme refolding assay. Thermal denaturation studies showed drastic reduction of denaturation temperature with increase in the degree of modification. Thermodynamic stability studies by urea denaturation assay reflected a decrease of transition midpoint. Quantitatively we found that ΔG° of native α-crystallin decreased from 21.6 kJ/mol to 10.4 kJ/mol due to 72 h modification by 10 mM methylglyoxal. The surface hydrophobicity of α-crystallin after MG modification, was found to be decreased. Circular dichroism spectroscopy revealed conversion of ß-sheet structure to random coil structure. Significant cross-linking was also observed due to methylglyoxal modification of human α-crystallin.

Atypical presentation of non-ossifying fibroma.

Non-ossifying fibroma is a common benign bone lesion but extensive involvement of almost whole of the shaft of right tibia is a rare presentation. The patient was a young lady of 35 years admitted at the department of Orthopaedics in Bangabandhu Sheikh Mujib Medical University (BSMMU) on June 2006 with pain and swelling of right distal tibia and unable to walk without support, was diagnosed clinico-radiologically as a case of fibrous dysplasia. The lady was undergone surgery and biopsy confirmed a case of non-ossifying fibroma. Within the follow up period of 28 months, the patient was well with full functional limb and the lesion was also healed radiologically.

Management of old Tendo Achilles injury by surgical reconstruction with Lindholm technique.

This prospective study was carried out in the department of orthopaedic surgery, Bangabandhu Sheikh Mujib Medical University from January 2006 to December 2007. Main aim of this study was to improve the power of planter flexion by reconstructive method with Lindholm technique to prevent walking disability. We had a study on 21 patients whose age range was 7 to 58 years. Mean age 34.19 years. Out of 21 cases male were 18(85.75%) and female were 3(14.25%). Chronocity of Tendo Achilles injury on average 2.64 (SD+/-1.08 month). Final clinical outcome of 21 cases 18 (85.75%) patients were satisfactory and 3(14.25%) were unsatisfactory. Lindholm technique is a good method of treatment for the management of Tendo Achilles injury was evident from this study. In Bangladesh toilet pan injury was more common. All patients were treated by surgical method of reconstruction by Lindholm technique.